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: a store sells chairs and tables. if the price of 2 chairs and 1 table is 60 % of the price of 1 chair and 2 tables, and the price of 1 table and 1 chair is $ 64, what is the price, in dollars, of 1 table ? ( assume that every chair has the same price and every table has the same price. )
Options: a. 48, b. 52, c. 54, d. 58, e. 56
Example Output: e

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: two pipes a and b can separately fill a tank in 12 and 15 minutes respectively. a third pipe c can drain off 45 liters of water per minute. if all the pipes are opened, the tank can be filled in 15 minutes. what is the capacity of the tank ?
Options: a. 399, b. 540, c. 772, d. 272, e. 121
Example Output:
b