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'.

Example 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
Example Output: d

Example Input: Problem: the average ( arithmetic mean ) of 4 positive integers is 50 . if the average of 2 of these integers is 35 , what is the greatest possible value that one of the other 2 integers can have ? 
Options: a ) 55 , b ) 65 , c ) 100 , d ) 109 , e ) 129
Example Output: e

Example Input: Problem: how many multiples of 5 are there between 50 and 500 ? 
Options: a ) 128 , b ) 91 , c ) 89 , d ) 61 , e ) 60
Example Output:
c