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.

Ex 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

Ex Output:
d


Ex Input:
Problem: if the wages of 6 men for 15 days be rs. 2100, then find the wages of for 12 days.
Options: a. rs. 2420, b. rs. 2500, c. rs. 2520, d. rs. 2020, e. rs. 2650

Ex Output:
c


Ex Input:
Problem: the average ( arithmetic mean ) of 7, 8, 10 and 11 equals the average of 2, 9, 13, and
Options: a. 7, b. 9, c. 10, d. 12, e. 13

Ex Output:

d