Task: Question Answering
Input (English): Problem: 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 20 people , 8 of whom are females , by how much does the index for the females exceed the index for the males in the group ? 
Options: a ) 0.05 , b ) 0.0625 , c ) 0.2 , d ) 0.25 , e ) 0.6
Output (English): c