15 different biology books and 8 different chemistry books lie on a shelf. In how many ways can a student pick 2 books of each type?	Choices.
A) 80
B) 160
C) 720
D) 2100
E) 2940

Rationale: "no . of ways of picking 2 biology books ( from 15 books ) = 15 c 2 = ( 15 * 14 ) / 2 = 105 no . of ways of picking 2 chemistry books ( from 8 books ) = 8 c 2 = ( 8 * 7 ) / 2 = 28 total ways of picking 2 books of each type = 105 * 28 = 2940 ( option e )"
Answer: E