For a group of n people, k of whom are of the same sex, the (n-k)/n expression yields an index for a certain phenomenon in group dynamics for members of that sex. For a group that consists of 25 people, 8 of whom are females, by how much does the index for the females exceed the index for the males in the group?  Choose the correct choice from the following choices: A) 0.05 B) 0.36 C) 0.2 D) 0.25 E) 0.6

Rationale: "index for females = ( 25 - 8 ) / 25 = 17 / 25 = 0.68 index for males = ( 25 - 17 / 25 = 8 / 25 = 0.32 index for females exceeds males by 0.68 - 0.32 = 0.36 answer : b"
Answer: B