Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

Ex Input:
Problem: the number of the members of a club is more than 50 and less than 80. when 4 people sit at a table, other people exactly divided to 8 - people groups ( 8 people sit at a table. or 7 - people groups ( 7 people sit at a table.. if the members are divided to 9 - people groups, how many people will be left ?
Options: a. 0, b. 2, c. 4, d. 6, e. 8

Ex Output:
d


Ex Input:
Problem: in n is a positive integer less than 200, and 14 n / 60 is an integer, then n has how many different positive prime factors s ?
Options: a. 2, b. 3, c. 5, d. 6, e. 8

Ex Output:
b


Ex Input:
Problem: a shopkeeper sold an article at $ 1800 with 20 % profit. then find its cost price ?
Options: a. $ 1000, b. $ 1500, c. $ 1850, d. $ 1600, e. $ 2000

Ex Output:

b