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 15: 00 there were 22 students in the computer lab. at 15: 03 and every three minutes after that, 3 students entered the lab. if at 15: 10 and every ten minutes after that 8 students left the lab, how many students were in the computer lab at 15: 44 ?
Options: a. 7, b. 14, c. 25, d. 27, e. 32

Ex Output:
e


Ex Input:
Problem: a light flashes every 30 seconds, how many times will it flash in ? of an hour ?
Options: a. 550, b. 600, c. 650, d. 700, e. 120

Ex Output:
e


Ex Input:
Problem: a certain telephone company offers two plans, a and b. under plan a, the company charges a total of $ 0.60 for the first 9 minutes of each call and $ 0.06 per minute thereafter. under plan b, the company charges $ 0.08 per minute of each call. what is the duration of a call, in minutes, for which the company charges the same amount under plan a and under plan b ?
Options: a. 3, b. 9, c. 15, d. 21, e. 30

Ex Output:

a