If n is the product of all the integers from 5 to 20, inclusive, what is the greatest integer k for which 2^k is a factor of n ? Pick one
A) 11  B) 12  C) 13  D) 14  E) 15

Rationale: 20 / 2 = 10 10 / 2 = 5 ans : 10 + 5 = 15 answer : e
Answer: E