There are 5 fictions and 6 non-fictions. How many cases are there such that 2 fictions and 2 non-fictions are selected from them? Choices
A) 90 B) 120 C) 150 D) 180 E) 200

Rationale: number of ways of selecting 2 fiction books = 5 c 2 number of ways of selecting 2 non fiction books = 6 c 2 5 c 2 * 6 c 2 = 10 * 15 = 150 answer : c
Answer: C