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'.

Ex Input:
Problem: the tax on a commodity is diminished by 40 % but its consumption is increased by 25 % . find the decrease percent in the revenue derived from it ? 
Options: a ) 18 % , b ) 72 % , c ) 25 % , d ) 12 % , e ) 52 %

Ex Output:
c


Ex Input:
Problem: marcella has 27 pairs of shoes . if she loses 9 individual shoes , what is the greatest number of matching pairs she could have left ? 
Options: a ) 22 , b ) 20 , c ) 19 , d ) 16 , e ) 15

Ex Output:
a


Ex Input:
Problem: exactly 3 / 7 of the people in the room are under the age of 21 , and exactly 5 / 14 of the people in the room are over the age of 65 . if the total number of the people in the room is greater than 50 and less than 100 , how many people in the room are under the age of 21 ? 
Options: a ) 21 , b ) 35 , c ) 39 , d ) 42 , e ) 65

Ex Output:

d