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: the sum of all the digits of the integers from 18 to 21 inclusive is 24 ( 1 + 8 + 1 + 9 + 2 + 0 + 2 + 1 = 24 ) . what is the sum t of all the digits of the integers from 0 to 99 inclusive ? 
Options: a ) 450 , b ) 810 , c ) 900 , d ) 1000 , e ) 1100

Ex Output:
c


Ex Input:
Problem: 3 times the first of 3 consecutive odd integers is 3 more than twice the third . the third integer is ? 
Options: a ) 15 , b ) 17 , c ) 19 , d ) 21 , e ) 26

Ex Output:
a


Ex Input:
Problem: if 9 a - b = 10 b + 50 = - 12 b - 2 a , what is the value of 11 a + 11 b ? 
Options: a ) - 4 , b ) - 2 , c ) 0 , d ) 2 , e ) 4

Ex Output:

c