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: a 270 metres long bullet train running at the speed of 120 kmph crosses another bullet train running in opposite direction at the speed of 80 kmph in 9 seconds. what is the length of the other bullet train ?
Options: a. 226, b. 230, c. 430, d. 310, e. 260

Ex Output:
b


Ex Input:
Problem: a grocer has a sale of rs. 5420, rs. 5660, rs. 6200, rs. 6350 and rs. 6500 for 5 consecutive months. find the sale he should have in the sixth month, so that he gets an average sale of rs. 6400 ?
Options: a. rs. 5870, b. rs. 8270, c. rs. 6020, d. rs. 6850, e. none of these

Ex Output:
b


Ex Input:
Problem: earl can stuff advertising circulars into envelopes at the rate of 36 envelopes per minutes and ellen requires a minutes and half to stuff the same number of envelops. working together, how long will it take earl and ellen to stuff 300 envelopes
Options: a. 6 minutes, b. 5 minutes, c. 7 minutes, d. 3 minutes, e. 4 minutes

Ex Output:

b