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: at a florist shop on a certain day, all corsages sold for either $ 20 or $ 30. if 10 of the corsages that sold for $ 30 had instead sold for $ 20, then the store ' s revenue from corsages that day would have been reduced by 20 percent. what was the store ' s actual revenue from corsages that day ?
Options: a. $ 200, b. $ 400, c. $ 500, d. $ 800, e. $ 1000

Ex Output:
c


Ex Input:
Problem: 11 is subtracted from 40 % of a number and results is 23. what is the number ?
Options: a. 160, b. 92, c. 88, d. 85, e. 34

Ex Output:
d


Ex Input:
Problem: two bullet trains of equal lengths take 10 seconds and 12 seconds respectively to cross a telegraph post. if the length of each bullet train be 120 metres, in what time ( in seconds ) will they cross each other travelling in opposite direction ?
Options: a. 11 sec., b. 15 sec., c. 12 sec., d. 17 sec., e. 19 sec.

Ex Output:

a