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 car is 15 minutes late by running at a speed of 4 / 5 th of its actual speed. the actual time taken by the car to cover that distance is :
Options: a. 30 minutes, b. 1 hour, c. 2 hours, d. 3 hours, e. none of these
Example Output: b

Example Input: Problem: a company produces 50000 bottles of water everyday. if a case can hold 25 bottles of water. how many cases are required by the company to hold its one day production
Options: a. 2000, b. 4500, c. 5000, d. 8000, e. 9000
Example Output: a

Example Input: Problem: if a: b: : 3: 7, then what is ( 5 a + 2 b.: ( a - 2 b. ?
Options: a. 57: 11, b. - 57: 11, c. 11: 10, d. - 29: 11, e. - 1: 10
Example Output:
d