In this task, you need to provide the correct option for a given problem from the provided options.

Example Input: Problem: a class has a ratio of 3 : 6 : 7 of children with red hair , blonde hair and black hair respectively . if the class has 9 kids with red hair , how many kids are there with black hair ?
Options: a ) 7 , b ) 6 , c ) 9 , d ) 21 , e ) 63
Example Output: d

Example Input: Problem: the ratio of the present ages of two friends is 2 : 3 and 6 years back , the ratio was 1 : 3 . what will be the ratio of their ages after 4 years ?
Options: a ) 1 : 4 , b ) 3 : 4 , c ) 1 : 2 , d ) 3 : 1 , e ) 3 : 2
Example Output: b

Example Input: Problem: 12 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 ?
Options: a ) 80 , b ) 160 , c ) 720 , d ) 1600 , e ) 1848
Example Output:
e