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: a, b, c can complete a piece of work in 24, 8,12 days. working together, they complete the same work in how many days ?
Options: a. 4, b. 4 / 5, c. 7 / 9, d. 10, e. 24 / 7
Example Output: a

Example Input: Problem: if a randomly selected positive single digit multiple of 3 is multiplied by a randomly selected prime number less than 20, what is the probability w that this product will be a multiple of 45 ?
Options: a. 1 / 32, b. 1 / 28, c. 1 / 24, d. 1 / 16, e. 1 / 14
Example Output: c

Example Input: Problem: what percent of 150 is 40 ?
Options: a. 0.25 %, b. 26.67 %, c. 25 %, d. 40 %, e. 250 %
Example Output:
b