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 the perimeter of a rectangular garden is 700 m, its length when its breadth is 100 m is ?
Options: a. 299 m, b. 777 m, c. 200 m, d. 250 m, e. 128 m
Example Output: d

Example Input: Problem: two trains are moving in opposite directions at 60 km / hr and 90 km / hr. their lengths are 1.15 km and 0.6 km respectively. the time taken by the slower train to cross the faster train in seconds is ?
Options: a. 42, b. 9, c. 7, d. 67, e. 15
Example Output: a

Example Input: Problem: a certain social security recipient will receive an annual benefit of $ 12,000 provided he has annual earnings of $ 9,360 or less, but the benefit will be reduced by $ 1 for every $ 3 of annual earnings over $ 9,360. what amount of total annual earnings would result in a 40 percent reduction in the recipient ' s annual social security benefit ? ( assume social security benefits are not counted as part of annual earnings. )
Options: a. $ 15,360, b. $ 17,360, c. $ 18,000, d. $ 21,360, e. $ 30,960
Example Output:
e