In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Ex Input:
Problem: a father said to his son , ` ` i was as old as you are at the present at the time of your birth ' ' . if the father ' s age is 52 years now , the son ' s age 5 years back was : 
Options: a ) a ) 14 , b ) b ) 67 , c ) c ) 56 , d ) d ) 21 , e ) e ) 34

Ex Output:
d


Ex Input:
Problem: find value of x : ( 422 + 404 ) ^ 2 − ( 4 × 422 × 404 ) = x . 
Options: a ) 234 , b ) 267 , c ) 324 , d ) 356 , e ) 577

Ex Output:
c


Ex Input:
Problem: find the average of all numbers between 1 and 13 which are divisible by 2 
Options: a ) 15 , b ) 21 , c ) 25 , d ) 30 , e ) 35

Ex Output:

b