TASK DEFINITION: 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.
PROBLEM: 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']

SOLUTION: a

PROBLEM: Problem: a walks at 10 kmph and 4 hours after his start, b cycles after him at 20 kmph. how far from the start does b catch up with a ?
Options: a. 100 km, b. 150 km, c. 80 km, d. 120 km, e. 200 km

SOLUTION: c

PROBLEM: Problem: working simultaneously and independently at an identical constant rate, 5 machines of a certain type can produce a total of x units of product p in 4 days. how many of these machines, working simultaneously and independently at this constant rate, can produce a total of 2 x units of product p in 2 days ?
Options: a. 11, b. 13, c. 15, d. 18, e. 20

SOLUTION:
e