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: what is the next number : 2 , 17 , 257 , __ 
Options: a ) 2977 , b ) 3837 , c ) 4097 , d ) 4847 , e ) 5387

Ex Output:
c


Ex Input:
Problem: of the final grades received by the students in a certain math course , 1 / 5 are a ' s , 1 / 4 are b ' s , 1 / 2 are c ' s , and the remaining 30 grades are d ' s . what is the number of students in the course ? 
Options: a ) 80 , b ) 110 , c ) 160 , d ) 600 , e ) 400

Ex Output:
d


Ex Input:
Problem: the average of first five multiples of 6 is ? 
Options: a ) 6 , b ) 18 , c ) 9 , d ) 5 , e ) 7

Ex Output:

b