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: the product of two numbers is 2028 and their h . c . f is 13 . the number of such pairs is : 
Options: a ) 1 , b ) 2 , c ) 3 , d ) 4 , e ) 5
Example Output: b

Example Input: Problem: if xy denotes x is raised to the power y , find the last two digits of 19413843 + 19614181 
Options: a ) 67 , b ) 97 , c ) 55 , d ) 32 , e ) 62
Example Output: e

Example Input: Problem: what is the least value of x . so that 21 x 57 is divisible by 3 . 
Options: a ) 2 , b ) 0 , c ) 1 , d ) 3 , e ) 4
Example Output:
b