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 probability of two events a and b are 0.25 and 0.40 respectively. the probability that both a and b occur is 0.15. the probability that neither a nor b occur is _________
Options: a. 0.45, b. 0.4, c. 0.5, d. 0.05, e. 0.6

Ex Output:
c


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: the mark up between ` ` normal plan ' ' price and ` ` premium plan ' ' price is 30 percent of the ` ` normal plan ' ' price. the markup is what percent of the ` ` premium plan ' ' price ? ( markup = difference between normal and premium price plans )
Options: a. 8 %, b. 20 %, c. 33 1 / 3 %, d. 45 %, e. 56 2 / 3 %

Ex Output:

c