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.

Example Input: Problem: a person ' s present age is two - fifth of the age of his mother. after 8 years, he will be one - half of the age of his mother. how old is the mother at present
Options: a. 38, b. 40, c. 42, d. 44, e. 45
Example Output: b

Example Input: Problem: there are 27 different 3 - digit integers that can be formed using only the digits 3, 4 and 5. if all 27 of the integers were listed, what would their sum be ?
Options: a. 11,888, b. 11,988, c. 12,088, d. 12,188, e. 12,288
Example Output: b

Example Input: Problem: a train 110 m long is running with a speed of 82 km / hr. in what time will it pass a man who is running at 6 km / hr in the direction opposite to that in which the train is going ?
Options: a. 7 sec, b. 6 sec, c. 8 sec, d. 4.5 sec, e. 2 sec
Example Output:
d