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

Example Input: Problem: in a certain alphabet , 16 letters contain a dot and a straight line . 30 letters contain a straight line but do not contain a dot . if that alphabet has 50 letters , all of which contain either a dot or a straight line or both , how many letters contain a dot but do not contain a straight line ? 
Options: a ) 4 , b ) 8 , c ) 12 , d ) 16 , e ) 20
Example Output: a

Example Input: Problem: in a college the ratio of the numbers of boys to the girls is 8 : 5 . if there are 160 girls , the total number of students in the college is ? 
Options: a ) 562 , b ) 356 , c ) 452 , d ) 416 , e ) 512
Example Output: d

Example Input: Problem: among 300 students , 56 % study sociology , 44 % study mathematics and 40 % study biology . if 30 % of students study both mathematics and sociology , what is the largest possible number of students who study biology but do not study either mathematics or sociology ? 
Options: a ) 30 , b ) 90 , c ) 120 , d ) 172 , e ) 188
Example Output:
b