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 average age of 8 men increases by 2 years when two women are included in place of two men of ages 20 and 22 years. find the average age of the women ?
Options: a. 87, b. 98, c. 30, d. 29, e. 37
Example Output: d

Example Input: Problem: at a certain university, 65 % of the professors are women, and 70 % of the professors are tenured. if 90 % of the professors are women, tenured, or both, then what percent of the men are tenured ?
Options: a. 25, b. 37.5, c. 50, d. 62.5, e. 75
Example Output: d

Example Input: Problem: if 5400 mn = k ^ 4, where m, n, and k are positive integers, what is the least possible value of 2 m + n ?
Options: a. 11, b. 18, c. 20, d. 25, e. 35
Example Output:
e