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 unit digit in the product ( 891 * 781 * 912 * 463 ) is : 
Options: a ) 2 , b ) 5 , c ) 6 , d ) 8 , e ) 10
Example Output: c

Example Input: Problem: the difference between two numbers is 2395 . when the larger number is divided by the smaller one , the quotient is 6 and the remainder is 15 . the smaller number is 
Options: a ) 120 , b ) 239 , c ) 476 , d ) 523 , e ) 526
Example Output: c

Example Input: Problem: the population of a city increases @ 4 % p . a . there is an additional annual increase of 4 % of the population due to the influx of job seekers , find the % increase in population after 2 years ? 
Options: a ) 14.64 % , b ) 15.64 % , c ) 16.64 % , d ) 17.64 % , e ) 18.64 %
Example Output:
c