8/21/2019 ER Licao 22

http://slidepdf.com/reader/full/er-licao-22 1/3

8/21/2019 ER Licao 22

http://slidepdf.com/reader/full/er-licao-22 2/3

8/21/2019 ER Licao 22

http://slidepdf.com/reader/full/er-licao-22 3/3