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.

Input: Consider 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

Output: e

Input: Consider Input: Problem: 40 is subtracted from 60 % of a number, the result is 50. find the number ?
Options: a. 150, b. 330, c. 277, d. 279, e. 712

Output: a

Input: Consider Input: Problem: a bookseller sells his books at a 20 % markup in price. if he sells a book for $ 36.00, how much did he pay for it ?
Options: a. $ 34.40, b. $ 34.00, c. $ 32.00, d. $ 30.00, e. $ 35.00
Output: d