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: if a / b = 1 / 3, b / c = 2, c / d = 1 / 2, d / e = 3 and e / f = 1 / 10, then what is the value of abc / def ?
Options: a. 27 / 4, b. 27 / 8, c. 3 / 4, d. 3 / 20, e. 1 / 4
Example Output: d

Example Input: Problem: what is the perimeter of a square field whose diagonal is 8 â ˆ š 2 ?
Options: a. 64 m, b. 32 m, c. 30 m, d. 16 m, e. 18 m
Example Output: b

Example Input: Problem: each of the products produced yesterday was checked by worker x or worker y. 0.5 % of the products checked by worker x are defective and 0.8 % of the products checked by worker y are defective. if the total defective rate of all the products checked by worker x and worker y is 0.65 %, what fraction of the products was checked by worker y ?
Options: a. 1 / 5, b. 1 / 2, c. 2 / 3, d. 1 / 4, e. 2 / 5
Example Output:
b