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: the diagonal of a rectangle is √ 41 cm and its area is 20 sq. cm. the perimeter of the rectangle must be :
Options: ['a. 18', 'b. 28', 'c. 38', 'd. 48', 'e. 58']

Output: a


Input: Consider Input: Problem: if x + y = 260, x - y = 200, for integers of x and y, y = ?
Options: a. 200, b. 230, c. 50, d. 115, e. 150

Output: b


Input: Consider Input: Problem: oil cans x and y are right circular cylinders and the height and radius of y are each 4 times those of x. if the oil in can x filled to capacity sells for $ 2, how much does the oil in y sell for if y is only half filled ?
Options: a. $ 60, b. $ 52, c. $ 63, d. $ 64, e. $ 68


Output: d