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: find value for x from below equation ? x + 1 = 4 
Options: a ) - 5 , b ) - 4 , c ) 4 , d ) 3 , e ) 2
Example Output: d

Example Input: Problem: if n is an integer , f ( n ) = f ( n - 1 ) - n and f ( 4 ) = 14 . what is the value of f ( 6 ) ? 
Options: a ) 3 , b ) 0 , c ) 1 , d ) 2 , e ) 4
Example Output: a

Example Input: Problem: if x + y = - 4 , and x = 6 / y , what is the value of x ^ 2 + y ^ 2 ? 
Options: a ) 10 , b ) 15 , c ) 6 , d ) 4 , e ) 5
Example Output:
d