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: car z travels 50 miles per gallon of gasoline when driven at a constant rate of 45 miles per hour, but travels 20 percent fewer miles per gallon of gasoline when driven at a constant rate of 60 miles per hour. how many miles does car z travel on 10 gallons of gasoline when driven at a constant rate of 60 miles per hour ?
Options: a. 320, b. 375.2, c. 400, d. 408.3, e. 440

Ex Output:
c


Ex Input:
Problem: in n is a positive integer less than 200, and 14 n / 60 is an integer, then n has how many different positive prime factors s ?
Options: a. 2, b. 3, c. 5, d. 6, e. 8

Ex Output:
b


Ex Input:
Problem: he average weight of 8 persons increases by 2.5 kg when a new person comes in place of one of them weighing 70 kg. what might be the weight of the new person ?
Options: a. 90 kg, b. 55 kg, c. 45 kg, d. 85 kg, e. 25 kg

Ex Output:

a