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.

Example 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
Example Output: c

Example Input: Problem: 2,7, 17,3, 11,19, 5,13, __
Options: a. 20, b. 21, c. 22, d. 23, e. 24
Example Output: d

Example Input: Problem: the radius of a wheel is 22.5 cm. what is the distance covered by the wheel in making 500 resolutions ?
Options: a. 708 m, b. 707.14 m, c. 774 m, d. 714 m, e. 744 m
Example Output:
b