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'.

Ex Input:
Problem: if a and b are the roots of the equation x 2 - 9 x + 20 = 0 , find the value of a 2 + b 2 + ab ? 
Options: a ) 57 , b ) 59 , c ) 61 , d ) 63 , e ) 65

Ex Output:
c


Ex Input:
Problem: how many 3 - digit numbers are divisible by 6 in all ? 
Options: a ) 149 , b ) 150 , c ) 151 , d ) 166 , e ) none

Ex Output:
b


Ex Input:
Problem: the operation is defined for all integers a and b by the equation ab = ( a - 1 ) ( b - 1 ) . if x 9 = 160 , what is the value of x ? 
Options: a ) 18 , b ) 15 , c ) 17 , d ) 19 , e ) 21

Ex Output:

e