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 “ a - number ” of a number x is defined as the ones digit of 2 ^ x . antony rolls a die with 6 sides labeled with the integers from 1 to 6 , each of which has an equal probability of landing face - up . he then takes 3 ^ a , where a is the a - number of the result of his die roll , and plots 3 ^ a on a number line as the point a . finally , he repeats this entire process , this time plotting the result as the point b . what is the probability that the distance between a and b is greater than the value of b ? 
Options: a ) 3 / 8 , b ) 13 / 36 , c ) 17 / 36 , d ) 19 / 36 , e ) 23 / 36
Example Output: b

Example Input: Problem: a man has rs . 400 in the denominations of one - rupee notes , 5 - rupee notes and 10 rupee notes . the number of notes of each denomination is equal . what is the total number of notes that he has ? 
Options: a ) 45 , b ) 60 , c ) 75 , d ) 90 , e ) 95
Example Output: c

Example Input: Problem: in a box of 12 pens , a total of 4 are defective . if a customer buys 3 pens selected at random from the box , what is the probability that neither pen will be defective ? 
Options: a ) 1 / 6 , b ) 2 / 55 , c ) 14 / 55 , d ) 12 / 55 , e ) 3 / 4
Example Output:
c