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 speed of the boat in still water in 12 kmph. it can travel downstream through 54 kms in 3 hrs. in what time would it cover the same distance upstream ?
Options: a. 8 hours, b. 6 hours, c. 4 hours, d. 5 hours, e. 9 hours
Example Output: e

Example Input: Problem: find the sum of first 89 odd numbers
Options: a. 7921, b. 4800, c. 7900, d. 4980, e. 4960
Example Output: a

Example Input: Problem: if 75 percent of a class answered the first question on a certain test correctly, 70 percent answered the second question on the test correctly, and 20 percent answered neither of the questions correctly, what percent answered both correctly ?
Options: a. 10 %, b. ( 8 ) 20 %, c. 30 %, d. 50 %, e. 65 %
Example Output:
e