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: 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
Example Output: e

Example Input: Problem: the cash realised on selling a 14 % stock is rs. 109.25, brokerage being 1 / 4 % is ?
Options: a. 366, b. 106, c. 102, d. 109, e. 122
Example Output: d

Example Input: Problem: the time taken by a man to row his boat upstream is twice the time taken by him to row the same distance downstream. if the speed of the boat in still water is 60 kmph, find the speed of the stream ?
Options: a. 18 kmph, b. 19 kmph, c. 21 kmph, d. 22 kmph, e. 20 kmph
Example Output:
e