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7/17/2019 trans funda

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-Nominal voice channel bandwidth is ___________.a. 20 to 30 kHzb. 0 to 3 kHzc. 4 kHzd. 55 kHz aboveans: c

-Echo suppressors are used on all communications system when the round trip pro

pagation time exceeds _____________.a. 50 msb. 30 msc. 100 msd. 1 msans: a

-A radio transmission line of 300 ohms impedance is to be connected to an anten

na having an input impedance of 150 ohms. What is the impedance of a quarter-wave matching line?a. 212 ohmsb. 250 ohmsc. 200 ohmsd. 150 ohmsans: a

- Quarter-wavelength line is used as ___________.a. impedance transformerb. lecher linec. transmission lined. harmonic suppressorans: a

-The transmission lines which can convey electromagnetic waves only in higher m

odes is usually calleda. coaxial cableb. waveguidec. power lines

d. twisted wire of telephone lineans: b-Why is nitrogen gas sometimes used in waveguide?a. To increase the distributed capacitanceb. To keep the waveguide dryc. To reduce the skin effect at the walls of the guided. To raise the guide's wave impedanceans: b

-Why is it impossible to use a waveguide at low radio frequencies?a. High dielectric lossb. Severe attenuation

c. Excessive radiationd. The size of the waveguideans: d

-How do you couple in and out of a waveguide?a. Wrap a coil of wire around one end of the waveguideb. Insertion of an E-probe into the waveguidec. Insertion of an H-loop into the waveguided. Both B and Cans: d


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-A rectangular waveguide is operating in the dominant TE(10) mode. The associat

ed flux lines are establisheda. transversely across the narrow dimension of the waveguideb. transversely across the wide dimension of the waveguidec. in the metal walls parallel to the direction of propagationd. in the metal walls perpendicular to the direction of propagationans: a

-For dominant mode of a rectangular waveguide, the distance between two instant

aneous consecutive positions of maximum field intensity (in a direction parallelto the walls of the waveguide) is referred to as half of thea. free-space wavelengthb. cutoff wavelength in the wide dimensionc. guide wavelengthd. group wavelengthans: c

-The guide wavelength, lambda g, in a rectangular waveguide isa. equal to the free-space wavelength at the cutoff frequencyb. equal to the free-space wavelength for the same signal frequencyc. less than the free-space wavelength at the cut-off frequencyd. greater than the free-space wavelength at the same signal frequencyans: d

- Using the TE(10) mode, microwave power can only be transmitted in free rectangular guide provideda. the wider dimension is less than one-half of the wavelength in free spaceb. the narrow dimension is less than one-quarter of the wavelength in free spa

cec. the wide dimension is greater than one-half of the guide wavelengthd. the wide dimension is greater than one-half of the wavelength in free space

ans: d

-If the signal frequency applied to a rectangular guide is increased and the do

minant mode is employed

a. the free space wavelength, lambda, is increasedb. the phase velocity, Vphi, increasedc. the guide wavelength is increasedd. the group velocity, Vg is increasedans: d

-If a 6 GHz signal is applied to a rectangular waveguide and the reflection ang

le, theta, is 20 degrees, what is the value of the guide wavelength, lambda g?a. 6.10 cmb. 5.32 cmc. 4.78 cmd. 5.00 cmans: b

-The inner dimensions of a rectangular waveguide are 1.75 cm by 3.5 cm. The cut

off wavelength for the dominant mode isa. 1.75 cmb. 3.5 cmc. 7.0 cmd. 0.4375 cmans: c

-A signal whose wavelength is 3.5 cm is being propagated along a guide whose in


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ner dimensions are 2 cm by 4 cm. What is the value of the guide wavelength, lambda g?a. 3.12 cmb. 3.89 cmc. 3.57 cmd. 6.30 cmans: b

-The frequency range over which a rectangular waveguide is excited in the domin

ant mode is limited toa. the difference between the frequency for which the reflection angle, theta,

is 90 degrees and the frequency for which theta is zero.b. the difference between the frequency for which the free-space wavelength is

equal to the cutoff value and the frequency for which the free-space wavelengthis equal to the guide wavelengthc. the difference between the frequency at which the cutoff wavelength is twic

e the narrow dimension.d. none of theseans: c

-If a rectangular waveguide is to be excited in the dominant mode, the E-probe

should be inserteda. at the sealed endb. at a distance of one quarter-wavelength from the sealed end

c. at a distance of one-half wavelength from the sealed endd. at a distance of three-quarters of a wavelength from the sealed endans: b

-A quarter-wave line is connected to an RF generator and is shorted out at the

far end. What is the input impedance to the line generator?a. a low value of resistanceb. a high value of resistancec. a capacitive resistance which is equal in the value to the line's surge imp

edanced. an inductive resistance which is equal to the value to the line's surge imp

edanceans: b

- If the SWR on a transmission line has a high value, the reason could bea. an impedance mismatch between the line and the load.b. that the line is nonresonantc. a reflection coefficient of zero at the loadd. that the load is matched to the lineans: a

-If a quarter-wave transmission line is shorted at one enda. there is minimum current at the shorted endb. the line behaves as a parallel-tuned circuit in relation to the generatorc. the line behaves as a series-tuned circuit in relation to the generatord. there is a minimum voltage at the shorted end.

ans: b-A 50-ohm transmission line is feeding an antenna which represents a 50 ohms re

sistive load. To shorten the line, the length must bea. any convenient valueb. an odd multiple of three-quarters of a wavelengthc. an odd multiple of half a wavelengthd. an even multiple of a quarter of a wavelengthans: a

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The outer conductor of the coaxial cable is usually groundeda. at the beginning and at the end of the cableb. only at the beginning of the cable and only at the end of the cablec. only at the end of the cabled. at the middle of the cableans: b

-A feature of an infinite transmission line is thata. its input impedance at the generator is equal to the line's surge impedance

b. its phase velocity is greater than the velocity of lightc. no RF current will be drawn from the generatord. the impedance varies at different positions on the lineans: a

-When the surge impedance of a line is matched to a load, the line willa. transfer maximum current to the loadb. transfer maximum voltage to the loadc. transfer maximum power to the loadd. have a VSWR equal to zeroans: c

-A lossless line is terminated by a resistive load which is not equal to the su

rge impedance. If the value of the reflection coefficient is 0.5, the VSWR is

a. 2b. 3c. 4d. 15ans: b

-Ratio of the mismatch between the antenna and the transmitter power.a. Standing wave patternb. Reflection coefficientc. SWRd. Index of refractionans: c

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Emission designation for a facsimilea. H3E and A4Eb. R3E and A4Ec. F4E and J3Ed. F3C and A3Eans: d

-Commonly used telephone wire.a. AWG #19b. AWG #18c. AWG #30d. AWG #33ans: a

-What is the distance traveled by a wave in the time of one cycle?a. Frequencyb. Hopc. Wavelengthd. Crestans: c

-The velocity factor is inversely proportional with respect to the _________.a. square of the dielectric constant


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b. square root of the dielectric constantc. dielectric constantd. square root of refractive indexans: b

-What circuit connects a balanced line to an unbalanced line?a. Stubb. Hybridc. Balund. Directional couplerans: c

-To connect a coaxial line to a parallel wire line, _________ is used.a. hybrid circuitb. balunc. directional couplerd. quarter-wave transformer matching circuitans: b

-What length for which the input power has been halved for a transmission line

with an attenuation of 6 dB/km?a. 1.5 kmb. 0.5 kmc. 63 km

d. 2 kmans: b-What is the wavelength in the waveguide with 4.5 GHz cut-off frequency excited

by 6.7 GHz?a. 0.196 mb. 0.336 mc. 0.136 md. 0.136 cmans: a

-A rectangular waveguide has dimensions of 3 cm x 5 cm. What is the dominant mo

de cut-off frequency?

a. 2 GHzb. 3 GHzc. 2.5 GHzd. 3.5 GHzans: b

-__________ are transmission lines which can convey electromagnetic waves onlyin higher order modes?a. Coaxial cablesb. Twisted pairs of telephone wirec. Power cablesd. Waveguidesans: d

-The amount of uncertainly in a system of symbols is also calleda. bandwidthb. lossc. entropyd. quantumans: c

-The twists in twisted wire pairsa. reduced electromagnetic interference


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b. occur at a 30-degree anglec. eliminate loadingd. were removed due to costans: a

-An example of bounded medium isa. coaxial cableb. waveguidec. fiber-optic cabled. all of the aboveans: d

-Loading means to the addition ofa. resistorsb. capacitorsc. bulletsd. inductanceans: d

-What is the most commonly used transmission line for high frequency applicatio

n?a. Two-wire balance lineb. Single wirec. Three-wire line

d. Coaxialans: d-The characteristic impedance of a transmission does not depend upon itsa. lengthb. conductor diameterc. conductor spacingd. dielectric materialans: a

-One of the following is not a common transmission line impedance.a. 50 ohmsb. 75 ohms

c. 120 ohmsd. 300 ohmsans: c

-For maximum absorption of power at the antenna, the relationship between the c

haracteristic impedance of the line Zo and the load impedance Zl should bea. Zo = Zlb. Zo > Zlc. Zo < Zld. Zo = 0ans: a

-The mismatch between antenna and transmission line impedance cannot be correct

ed for bya. using LC matching networkb. adjusting antenna lengthc. using a balund. adjusting the length of transmission lineans: d

-____________ is a pattern of voltage and current variations along a transmission line not terminated in its characteristic impedance.a. an electric field


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b. radio wavesc. standing wavesd. a magnetic fieldans: c

-Which is the desirable SWR on a transmission line?a. 0b. 1c. 2d. infinityans: b

-A 50 ohms coax is connected to a 73-ohms antenna. What is the SWR?a. 0.685b. 1c. 1.46d. 2.92ans: c

-What is the most desirable reflection coefficient?a. 0b. 0.5c. 1d. infinity

ans: a-What is the ratio expressing the percentage of incident voltage reflected on a

transmission line?a. Velocity factorb. Standing-wave ratioc. Reflection coefficientd. Line efficiencyans: c

-The minimum voltage along a transmission line is 260 V, while the maximum is 3

90 V sub 1. The SWR isa. 0.67

b. 1.0c. 1.2d. 1.5ans: d

-One meter is one wavelength at a frequency ofa. 150 MHzb. 164 MHzc. 300 MHzd. 328 MHzans: c

-At very high frequencies. Transmission lines act as

a. tuned circuitsb. antennasc. insulatorsd. resistorsans: b

-A shorted quarter-wave line at the operating frequency acts like a/ana. capacitorb. inductorc. series resonant circuit


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d. parallel resonant circuitans: d

-A shorted half-wave line at the operating frequency acts like a/ana. capacitorb. inductorc. series resonant circuitd. parallel resonant circuitans: c

-A medium least susceptible to noise?a. Shielded pairb. Twisted pairc. Fiber-opticd. Coaxialans: d

-A medium most widely used in LANs?a. Parallel-wire lineb. Twisted pairc. Fiber-opticd. Coaxialans: b

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The most commonly used transmission line in television system.a. Parallel-wire lineb. Coaxial cablec. Waveguided. Open-wire with ceramic supportsans: b

-The impedance of a TV transmission line depends on several factors. Which is n

ot one of those factors?a. Diameterb. Length of the wirec. Dielectric materiald. Separation between conductors

ans: b-DC blocks are used in coaxial transmission line for the purpose ofa. passing DC while blocking ACb. passing AC voltage but prevent DCc. preventing AC voltage from reaching the pre-amplifierd. preventing AC power supply voltage from being shorted by a balun or band sp

litterans: d

-_________ is a type of interference caused by off-air TV channels 2 and 4, plus a satellite dish operating on channel 3.a. Adjacent channel interference

b. Ghostc. Co-channel interferenced. Crosstalkans: a

-Dithering (in TVRO communications) is a process fora. reducing the effect of noise on the TVRO video signalb. centering the video fine tuning on TVRO channelsc. moving the feedhorn rotor to the precise angled. moving the actuator exactly onto the desired satellite beam


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ans: a-A network that has an input of 75 dB and an output of 35dB. The loss of the ne

twork is ______________.a. -40 dBb. 40 dBc. 40 dBmd. -40 dBmans: b

-Important useful quantities describing waveforms.a. Time and frequencyb. Voltage and currentc. Frequency and voltaged. Power and frequencyans: c

-Halving the power meansa. 6-dB gainb. 3-dB lossc. 3-dB gaind. 6-dB lossans: b

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One neper (Np) is how many decibels?a. 8.866b. 8.686c. 8.688d. 8.868ans: b

-A signal is amplified 100 times in power. The dB gain isa. 20 dBb. 119 dBc. 15 dBd. 25 dBans: a

- Which of the following is used to measure SWR?a. Spectrum analyzerb. Reflectometerc. Oscilloscoped. Multimeterans: b

-214-056 twin lead which is commonly used for TV lead-in has a characteristics

impedance ofa. 52 ohmsb. 75 ohmsc. 600 ohms

d. 300 ohmsans: d

-What is the characteristic impedance of a transmission line which is to act as

a quarterwave matching transformer between a 175 ohms transmission line and 600ohms load?a. 300.04 ohmsb. 324.04 ohmsc. 310.04 ohmsd. 320.04 ohms


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ans: b-What is the EIRP in dBW of a 50 dB antenna connected to transmitter with an ou

tput of 10 kW through a transmission line with a loss of 5 dB?a. 85 dBWb. 955 dBWc. 90 dBWd. 80 dBWans: a

-A coaxial cable is a good example of a/ana. unbounded mediumb. transmission channelc. non-metallic mediumd. bounded mediumans: d

-If a quarterwave transformer is required to match a 180ohms load to a transmis

sion line w/ an impedance of 300ohms, what should be the char. impedance of thematching transformer? Assume that the matching transformer is to be connected directly to the loada. 180 ohmsb. 232 ohmsc. 300 ohms

d. 480 ohmsans: b-A transmitter of 100 W RF power output, 100% modulated is operating on a frequ

ency of 169 MHz. The antenna transmission line consists of a 50 ohms coaxial cable 150 ft. long. The coaxial inner conductor outer diameter is 0.162 in. Determine the outside diameter of the outer conductor if the outer conductor has a thickness of 0.05 in (Assume k = 1).a. 1.0 inb. 0.9 inc. 0.7 ind. 0.5 inans: d

- A transmitter of 100 W RF power output, 100% modulated is operating on a frequency of 169 MHz. The antenna transmission line consists of a 50 ohms coaxial cable 150 ft. long. The coaxial inner conductor outer diameter is 0.162 in. The outer conductor has a thickness of 0.05 in (Assume k = 1). In the problem, calculate the line current.a. 1.7 Ab. 1.3 Ac. 1.5 Ad. 1.0 Aans: a

-A transmitter of 100 W RF power output, 100% modulated is operating on a frequ

ency of 169 MHz. The antenna transmission line consists of a 50 ohms coaxial cable 150 ft. long. The coaxial inner conductor outer diameter is 0.162 in. The outer conductor has a thickness of 0.05 in (Assume k = 1). Determine the total attenuation of the line in the problem.a. 2.0 dBb. 1.5 dBc. 2.5 dBd. 1.0 dBans: b

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What is the max. subscriber loop length, in ft., of a telephone system if thesignaling resistance is 1800 ohms using a tel. cable pair of gauge # 26 with a loop resistance of 83.5 ohms per 1000 ft. Assume the telephone set resistance isequal to 200 ohms.a. 15,161.7 feetb. 19,161 feetc. 15,300 feetd. 20,000 feetans: b

-If the same subscriber loop above limits the voice attenuation to a maximum of

6 dB, what is the maximum allowable subscriber loop length, in feet, using thesame gauge # 26 telephone wire? Assume a 2.7 dB loss per mile.a. 20,000 ftb. 13,900 ftc. 15,280 ftd. 11,733 ftans: d

-The input is 0.1 W and the network gain is 13 dB, the output isa. 2.0 Wb. 2.5 Wc. 1.5 Wd. 1.8 W

ans: a-Known as one-tenth of a neper.a. dBb. dBmc. dBpd. dNpans: d

-The input impedance of a quarterwave short-circuited transmission line at its

resonant frequency isa. 0 ohmsb. infinite or an open circuit

c. ohmsd. 70 ohmsans: b

-The ratio of the largest rms value to the smallest rms value of the voltage in

the line is calleda. SWRb. ISWRc. VSWRd. Coefficient of reflectionans: c

-An open-wire, two-wire transmission line is to be connected to a dipole antenn

a through a quarter-wave matching stub. At a frequency of 10 MHz, compute the length of the dipolea. 20 mb. 7.5 mc. 15 md. 25 mans: c

-An open-wire, two-wire transmission line is to be connected to a dipole antenn

a through a quarter-wave matching stub. At a frequency of 10 MHz, compute the le


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ngth of the quarterwave stub.a. 15 mb. 7.5 mc. 20 md. 25 mans: b

-To find the char. Impedance of a coaxial cable, measurements are made with (a)

the far end open circuited & (b) far end short circuited, the corresponding readings being a) Ro=3ohms & Xc=55ohms, capacitive b) Rs=10ohms & Xl=90ohms, inductive What is the characteristic impedance, Zo, of the line?a. 75.7 - j2.0 ohmsb. 70.7 + j1.19 ohmsc. 87.5 - j5 ohmsd. 70.7 - j1.97 ohmsans: d

-A TV antenna receives a signal measured at 200 V and is immediately amplified b

y a pre-amplifier with a 15 dB gain. This amplified signal then passes through acoaxial cable with 3 dB loss, what is the resulting input to the TV set, in dBmV?a. 1.98b. 13.98c. -1.98

d. -13.98ans: c-The characteristic impedance of a transmission line does not depend upon its _

_________.a. conductor spacingb. conductor diameterc. lengthd. conductor radiusans: c

-What does a power difference of -3 dB mean?a. a loss of one third of the power

b. a loss of one half of the powerc. a loss of three watts of the powerd. no significant changeans: b

-Which of the following is an advantage of the balance transmission line?a. Easy installationb. Outer shield eliminates radiation lossesc. Low attenuationd. None of theseans: c

-Waveguides are used mainly for microwave transmission because

a. they are bulky at lower frequenciesb. losses are heavy at lower frequenciesc. they depend on straight line propagationd. no generators are powerful enough to excite themans: d

-The input is 1 W and the network loss is 27 dB, the output isa. 1 mWb. 3 mWc. 2 mW


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d. 4 mWans: c

-A combiner has two inputs + 30 dBm and + 30 dBm, what is the resultant output?

a. + 36 dBmb. + 30 dBmc. + 60 dBmd. + 33 dBmans: d

-The ratio of the smallest to the largest rms current value is calleda. SWRb. VSWRc. ISWRd. Coefficient of reflectionans: c

-If the ratio of the maximum current to the minimum current in a transmission l

ine is 2:1 then the ratio of maximum voltage to minimum voltage isa. 4:1b. 1:2c. 1:4d. 2:1

ans: d-Two wires of 600 ohms characteristic impedance is to be constructed out of a n

umber 12 wire (81 mils). Find the attenuation of the line at 0.6 GHz per 100 feet length.a. 0.05 dBb. 0.55 dBc. 0.44 dBd. 0.35 dBans: c

-Two wires of 600 ohms characteristic impedance is to be constructed out of a n

umber 12 wire (81 mils). Determine the spacing between wires from center to cent

er.a. 6 inb. 4 inc. 5 ind. 3 inans: a

-A lossless transmission line has a shunt capacitance of 100 nF/m and a series

inductance of 4 mH/m. What is the characteristic impedance?a. 500 ohmsb. 400 ohmsc. 300 ohmsd. 200 ohms

ans: d-A ten times power change in transmission system is equivalent toa. 10 dBmb. 10 dBc. 20 dBd. 100 dBans: b

-A type of transmission line employed where balanced properties are required.


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a. Balunb. Parallel-wire linec. Coaxial lined. Quarterwave lineans: b

-What is the characteristic impedance of a transmission line which has a capaci

tance of 40 nF/ft and an inductance of 0.5 mH/fta. 111.8 ohmsb. 110.8 ohmsc. 112.8 ohmsd. 109.8 ohmsans: a

-The input power to a loss-free cable is 5W. If the reflected power is 7 dB dow

n on the incident power, the output power to the load isa. 4 Wb. 5 Wc. 6 Wd. 7 Wans: a

-To be properly matched the ratio of a maximum voltage along a transmission lin

e should be equal to

a. 1b. 10c. 50d. 2ans: a

-A coaxial line with an outer diameter of 6 mm has a 50 ohms characteristic imp

edance. If the dielectric constant of the insulation is 1.60, calculate the inner diameter.a. 2.09 cmb. 2.09 inc. 2.09 mmd. 2.09 mm

ans: c-If an amplifier has equal input and output impedances, what voltage ratio does

the gain of 50 dB represent?a. 316.2b. 325.2c. 320.1d. 315.0ans: a

-What is the inductance per foot of a cable that has a capacitance of 50 pF/ft

and a characteristic impedance of 60 ohms?a. 0.167 H/ft

b. 0.178 H/ftc. 0.19 H/ftd. 0.18 H/ftans: d

-The ratio between the energy absorbed by a surface to the total energy receive

d by the surface.a. Reflection coefficientb. Absorption coefficientc. Linear coefficient


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d. Thermal coefficientans: b

-When the diameter of the conductors of a 2 wire transmission line is held cons

tant, the effect of decreasing the distance between the conductors isa. increase the surge impedanceb. increase the radiation resistancec. decrease the SWRd. decrease the impedanceans: d

-The higher the gauge number of a conductora. the bigger the diameterb. the higher the resistance or the smaller the diameterc. the higher the resistanced. none of theseans: b

-A short length of transmission line used to reduce/eliminate standing waves in

the main transmission line.a. Stubb. Balunc. lambda/4 transformerd. Slot

ans: c-Ratio of reflected power to incident power?a. Incidenceb. Reflectancec. Reflection indexd. None of theseans: b

-A quarter wave transformer is used to match a 600 ohms load antenna to a line

of 52 ohms impedance, the characteristic impedance of the matching transformer isa. 200 ohms

b. 150 ohmsc. 176 ohmsd. 300 ohmsans: d

-What is the capacitance of 55 miles # 44 copper wire spaced 18 inches? From wi

re tables, # 44 wire has a radius to 0.10215 in.a. 0.476 Fb. 0.476 nFc. 0.476 pFd. 0.476 fFans: a

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A two-wire transmission line consists of No. 12 wire AWG (81 mils). The distance between wire centers is 10 inches. What is the characteristic impedance of the line?a. 650 ohmsb. 300 ohmsc. 600 ohmsd. 660 ohmsans: d

-A two-wire transmission line consists of No. 12 wire AWG (81 mils). The distan


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ce between wire centers is 10 inches. What is the attenuation in dB per 100 ft.of the line for a frequency of 4 MHz?a. 0.05b. 0.03c. 0.04d. 0.06ans: b

-What is the SWR when a transmission line is terminated in a short circuit?a. Zerob. Onec. Infinited. Indeterminateans: c

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