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: find the greatest number which leaves the same remainder when it divides 16, 46 and 82.
Options: a. 18, b. 8, c. 12, d. 16, e. none of these
Example Output: e

Example Input: Problem: a movie buff buys movies on dvd and on blu - ray in a ratio of 13: 4. if she returns 2 blu - ray movies, that ratio would change to 7: 2. if she buys movies on no other medium, what was the original number of movies purchased ?
Options: a. 22, b. 28, c. 77, d. 99, e. 119
Example Output: e

Example Input: Problem: a man took a loan at rate of 12 % per annum simple interest. after 3 years he had to pay 7200 interest. the principal amount borrowed by him was.
Options: a. rs 14000, b. rs 15000, c. rs 16000, d. rs 20000, e. none of these
Example Output:
d