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: ages of two persons differ by 20 years . if 6 year ago , the elder one be 3 times as old the younger one , find their present age 
Options: a ) 12,28 , b ) 14,30 , c ) 16,36 , d ) 18,34 , e ) 19,34

Output: c


Input: Consider Input: Problem: what is the average of first 21 multiples of 6 ? 
Options: a ) a ) 66 , b ) b ) 77 , c ) c ) 79 , d ) d ) 81 , e ) e ) 82

Output: a


Input: Consider Input: Problem: find ( 7 x + 6 y ) / ( x - 2 y ) if x / 2 y = 3 / 2 ? 
Options: a ) 24 , b ) 25 , c ) 26 , d ) 27 , e ) 29


Output: d