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.

Input: Consider 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

Output: d


Input: Consider Input: Problem: a and b invests rs. 2500 and rs. 4000 respectively in a business. if a doubles his capital after 6 months. in what ratio should a and b divide that year ' s profit ?
Options: a. 11: 5, b. 15: 16, c. 15: 2, d. 9: 9, e. 11: 1

Output: b


Input: Consider Input: Problem: the area of a square field is 7201 sq m. how long will a lady take to cross the field diagonally at the rate of 2.4 km / hr ?
Options: ['a. 2 min', 'b. 3 min', 'c. 4 min', 'd. 5 min', 'e. 6 min']


Output: b