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: how many positive even integers less than 100 contain digits 5 or 7 ?
Options: a. 10, b. 17, c. 18, d. 19, e. 20

Ex Output:
a


Ex Input:
Problem: by selling 20 pencils for a rupee a man loses 30 %. how many for a rupee should he sell in order to gain 30 % ?
Options: a. 8.56, b. 10.75, c. 14.5, d. 16.5, e. 11.4

Ex Output:
b


Ex Input:
Problem: a motorcyclist started riding at highway marker a, drove 120 miles to highway marker b, and then, without pausing, continued to highway marker c, where she stopped. the average speed of the motorcyclist, over the course of the entire trip, was 45 miles per hour. if the ride from marker a to marker b lasted 3 times as many hours as the rest of the ride, and the distance from marker b to marker c was half of the distance from marker a to marker b, what was the average speed, in miles per hour, of the motorcyclist while driving from marker b to marker c ?
Options: a. 40, b. 45, c. 50, d. 55, e. 60

Ex Output:

e