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 48 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. 6 hours
Example Output: e

Example Input: Problem: a certain sum is invested at simple interest at 18 % p. a. for two years instead of investing at 12 % p. a. for the same time period. therefore the interest received is more by rs. 300. find the sum ?
Options: a. 7000, b. 2500, c. 2778, d. 2800, e. 2791
Example Output: b

Example Input: Problem: the pinedale bus line travels at an average speed of 60 km / h, and has stops every 5 minutes along its route. yahya wants to go from his house to the pinedale mall, which is 8 stops away. how far away, in kilometers, is pinedale mall away from yahya ' s house ?
Options: a. 20 km, b. 30 km, c. 40 km, d. 50 km, e. 60 km
Example Output:
c