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: cost is expressed by the formula tb ^ 4. if b is doubled, the new cost w is what percent of the original cost ?
Options: a. w = 200, b. w = 600, c. w = 800, d. w = 1600, e. w = 50
Example Output: d

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: find the value of x in ( x + 1 ) / ( x + 3 ) = 5
Options: a. 2.5, b. - 2.5, c. 3.0, d. 3.5, e. - 3.5
Example Output:
e