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 a sum for 1 st 7 prime number ' s ? 
Options: a ) 25 , b ) 28 , c ) 58 , d ) 34 , e ) 36
Example Output: c

Example Input: Problem: if 4 xz + yw = 3 and xw + yz = 6 , what is the value of the expression ( 2 x + y ) ( 2 z + w ) ? 
Options: a ) 9 . , b ) 12 . , c ) 15 . , d ) 16 , e ) 18 .
Example Output: c

Example Input: Problem: the average ( arithmetic mean ) of 4 different integers is 72 . if the largest integer is 90 , what is the least possible value of the smallest integer ? 
Options: a ) 1 , b ) 19 , c ) 21 , d ) 30 , e ) 33
Example Output:
c