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 7 a - 3 b = 10 b + 50 = - 12 b - 2 a , what is the value of 9 a + 9 b ? 
Options: a ) - 9 , b ) - 6 , c ) 0 , d ) 6 , e ) 9

Ex Output:
c


Ex Input:
Problem: 11 + 12 + 13 + . . . 51 + 52 = ? 
Options: a ) 1361 , b ) 1362 , c ) 1323 , d ) 1364 , e ) 1365

Ex Output:
c


Ex Input:
Problem: n is the greatest number which divides 1305 , 4665 and 6905 and gives the same remainder in each case . what is the sum of the digits in n ? 
Options: a ) 23 , b ) 28 , c ) 4 , d ) 1 , e ) 25

Ex Output:

c