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: excluding stoppages, the average speed of a bus is 60 km / hr and including stoppages, the average speed of the bus is 40 km / hr. for how many minutes does the bus stop per hour ?
Options: a. 18 min, b. 17 min, c. 19 min, d. 20 min, e. 21 min

Output: d


Input: Consider Input: Problem: it is only in the second option we find the sentence a in continuation with the opening sentence d. sentence a alone explains, why the fear has such enormous effect on the human beings.
Options: a. 28, b. 99, c. 728, d. 27, e. 271

Output: b


Input: Consider Input: Problem: sophia finished 2 / 3 of a book. she calculated that she finished 30 more pages than she has yet to read. how long is her book ?
Options: a. a. 90, b. b. 150, c. c. 130, d. d. 190, e. e. 210


Output: a