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 train 510 m long is running at a speed of 45 km / hr. in what time will it pass a bridge 140 m long ?
Options: a. 40, b. 52, c. 26, d. 21, e. 14

Ex Output:
b


Ex Input:
Problem: the ratio of the present age of viju to that of aju is 7: 2. 4 years from now, the ratio of the ages of viju to aju will be 5: 2. what was viju age 5 years ago ? ( rbi assistant 2015 )
Options: a. 24, b. 18, c. 12, d. 16, e. 13

Ex Output:
d


Ex Input:
Problem: what will be the compound interest on a sum of rs. 29,000 after 3 years at the rate of 12 % p. a. ?
Options: a. s. 11123.77, b. s. 11742.91, c. s. 11123.20, d. s. 10123.28, e. s. 10123.21

Ex Output:

b