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: a high school has 400 students 1 / 2 attend the airthmetic club , 5 / 8 attend the biology club and 3 / 4 attend the chemistry club . 1 / 8 attend all 3 clubs . if every student attends at least one club how many students attend exactly 2 clubs . 
Options: a ) 300 , b ) 200 , c ) 250 , d ) 150 , e ) 160
Example Output: c

Example Input: Problem: how many integers between 1 and 10 ^ 16 are such that the sum of their digits is 2 ? 
Options: a ) 106 , b ) 116 , c ) 126 , d ) 136 , e ) 146
Example Output: d

Example Input: Problem: if xy > 0 , 1 / x + 1 / y = 6 , and 1 / xy = 5 , then ( x + y ) / 6 = ? 
Options: a ) 1 / 25 , b ) 1 / 6 , c ) 1 / 5 , d ) 5 , e ) 6
Example Output:
c