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: 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

Ex Output:
d

Ex Input:
Problem: find large number from below question the difference of two numbers is 1000. on dividing the larger number by the smaller, we get 10 as quotient and the 10 as remainder
Options: a. 1234, b. 1110, c. 1456, d. 1200, e. 1600

Ex Output:
b

Ex Input:
Problem: at a certain restaurant, the average ( arithmetic mean ) number of customers served for the past x days was 85. if the restaurant serves 120 customers today, raising the average to 90 customers per day, what is the value of x ?
Options: a. 2, b. 5, c. 6, d. 15, e. 30

Ex Output:
c