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: 1 men takes 37 $ to eat a pizza in restaurant such that it have discount multiple of 4 if u eat more pizza. discount increase by multiple of 4 every pizza u eat. for 1 pizza 0 % off. for 2 pizza % off for 3 pizza 8 % off. pizza without discount is 10 $. how much that man eats the pizza.
Options: a. 2, b. 3, c. 4, d. 5, e. 6

Ex Output:
b


Ex Input:
Problem: 10, 1000, 100000, 10000000....
Options: a. 100, 000,000, b. 1,000, 000,000, c. 1, 000,000, 000,000, d. 100, e. 1, 000,000

Ex Output:
b


Ex Input:
Problem: arun and tarun can do a work in 10 days. after 4 days tarun went to his village. how many days are required to complete the remaining work by arun alone. arun can do the work alone in 30 days.
Options: a. 16 days., b. 17 days., c. 18 days., d. 19 days., e. 20 days.

Ex Output:

c