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: a card game called “ high - low ” divides a deck of 52 playing cards into 2 types, “ high ” cards and “ low ” cards. there are an equal number of “ high ” cards and “ low ” cards in the deck and “ high ” cards are worth 2 points, while “ low ” cards are worth 1 point. if you draw cards one at a time, how many ways can you draw “ high ” and “ low ” cards to earn 7 points if you must draw exactly 5 “ low ” cards ?
Options: a. 6, b. 2, c. 3, d. 4, e. 5

Ex Output:
a


Ex Input:
Problem: buses a and b start from a common bus stop x. bus a begins to travel in a straight line away from bus b at a constant rate of 30 miles per hour. one hour later, bus b begins to travel in a straight line in the exact opposite direction at a constant rate of 50 miles per hour. if both buses travel indefinitely, what is the positive difference, in minutes, between the amount of time it takes bus b to cover the exact distance that bus a has covered and the amount of time it takes bus b to cover twice the distance that bus a has covered ?
Options: a. 36, b. 84, c. 132, d. 144, e. 180

Ex Output:
b


Ex Input:
Problem: in a fuel station the service costs $ 1.75 per car, every liter of fuel costs 0.65 $. assuming that a company owns 12 cars and that every fuel tank contains 50 liters and they are all empty, how much money total will it cost to fuel all cars ?
Options: a. 320 $, b. 380 $, c. 420 $, d. 450 $, e. 411 $

Ex Output:

e