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: what is the total number of integers between 200 and 500 that are divisible by 25 ?
Options: a. 20, b. 25, c. 14, d. 15, e. 18
Example Output: d

Example Input: Problem: what is the greatest positive integer e such that 3 ^ e is a factor of 9 ^ 10 ?
Options: a. e = 5, b. e = 9, c. e = 10, d. e = 20, e. 30
Example Output: d

Example Input: Problem: the present population of a town is 3744. population increase rate is 20 % p. a. find the population of town before 2 years ?
Options: a. 2500, b. 2600, c. 3500, d. 3600, e. 2050
Example Output:
b