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: x varies inversely as square of y . given that y = 3 for x = 1 . the value of x for y = 6 will be equal to :
Options: a ) 3 , b ) 6 , c ) 1 / 4 , d ) 1 / 3 , e ) 9

Ex Output:
c

Ex Input:
Problem: a number is doubled and 5 is added . if the resultant is trebled , it becomes 123 . what is that number ?
Options: a ) 12 , b ) 29 , c ) 27 , d ) 18 , e ) 99

Ex Output:
d

Ex Input:
Problem: a certain list consists of 21 different numbers . if n is in the list and n is 6 times the average ( arithmetic mean ) of the other 20 numbers in the list , then n is what fraction of the sum of the 21 numbers in the list ?
Options: a ) 1 / 20 , b ) 1 / 6 , c ) 1 / 5 , d ) 3 / 13 , e ) 5 / 21

Ex Output:
d