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: evaluate 64 / . 08 
Options: a ) 800 , b ) 500 , c ) 505 , d ) none of these , e ) 506
Example Output: a

Example Input: Problem: if x / y = 7 / 3 , then ( x + y ) / ( x - y ) = ? 
Options: a ) 5 , b ) 5 / 2 , c ) - 1 / 6 , d ) - 1 / 5 , e ) - 5
Example Output: b

Example Input: Problem: the average age of 30 students in a class is 10 years . if teacher ' s age is also included then average increases 1 year then find the teacher ' s age ? 
Options: a ) 59 , b ) 55 , c ) 61 , d ) 41 , e ) 36
Example Output:
d