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'.

Input: Consider Input: Problem: village x has a population of 72000 , which is decreasing at the rate of 1200 per year . village y has a population of 42000 , which is increasing at the rate of 800 per year . in how many years will the population of the two villages be equal ? 
Options: a ) 15 , b ) 19 , c ) 11 , d ) 18 , e ) 13

Output: a


Input: Consider 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

Output: d


Input: Consider Input: Problem: if the average of 6 digits is 16 and the average of 4 of them is 10 , calculate the average of the remaining 2 numbers ? 
Options: a ) 36 , b ) 35 , c ) 28 , d ) 33 , e ) 21


Output: c