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: if two of the 4 expressions x + y , x + 5 y , x - y , and 5 x - y are chosen at random , what is the probability w that their product will be of the form of x ^ 2 - ( by ) ^ 2 , where b is an integer ? 
Options: a ) 1 / 2 , b ) 1 / 3 , c ) 1 / 4 , d ) 1 / 5 , e ) w = 1 / 6

Output: e


Input: Consider Input: Problem: what is the next number 12 13 15 17 111 113 117 119 123 129 ? 
Options: a ) 154 , b ) 220 , c ) 129 , d ) 131 , e ) 224

Output: d


Input: Consider Input: Problem: if a farmer sells 15 of his goats , his stock of feed will last for 4 more days than planned , but if he buys 20 more goats , he will run out of feed 3 days earlier than planned . if no goats are sold or bought , the farmer will be exactly on schedule . how many goats does the farmer have ? 
Options: a ) 12 , b ) 24 , c ) 48 , d ) 60 , e ) 55


Output: d