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: 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: ages of two persons differ by 20 years. if 6 year ago, the elder one be 3 times as old the younger one, find their present age
Options: a. 12,28, b. 14,30, c. 16,36, d. 18,34, e. 19,34

Ex Output:
c


Ex Input:
Problem: 864.942 - ? + 45.76 = 547.905
Options: a. a. 899.015, b. b. 752.804, c. c. 714.642, d. d. 362.797, e. of these

Ex Output:

d