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: the difference between compound and simple interest on a certain sum of money for 3 years at 6 2 / 3 % p . a is rs . 184 . find the sum ? 
Options: a ) 33772 , b ) 26782 , c ) 26788 , d ) 13500 , e ) 27761
Example Output: d

Example Input: Problem: a father said his son , ` ` i was as old as you are at present at the time of your birth . ` ` if the father age is 32 now , the son age 5 years back was 
Options: a ) 11 , b ) 17 , c ) 11 , d ) 19 , e ) 99
Example Output: a

Example Input: Problem: joan took out a mortgage from hel local bank . each monthly mortgage payment she makes must be triple the amount of the previous month ' s payment . if her first payment is $ 100 , and the total amount she must pay back is $ 2952400 , how many months will it take joan to pay back her mortgage ? 
Options: a ) 6 , b ) 8 , c ) 10 , d ) 11 , e ) 13
Example Output:
c