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.
--------
Question: Problem: a man swims downstream 36 km and upstream 18 km taking 3 hours each time, what is the speed of the man in still water ?
Options: a. 7, b. 8, c. 9, d. 2, e. 4

Answer: c


Question: Problem: a rectangular tiled patio is composed of 96 square tiles. the rectangular patio will be rearranged so that there will be 2 fewer columns of tiles and 4 more rows of tiles. after the change in layout, the patio will still have 96 tiles, and it will still be rectangular. how many rows are in the tile patio before the change in layout ?
Options: a. 5, b. 6, c. 8, d. 13, e. 28

Answer: c


Question: Problem: the curved surface of a sphere is 64 π cm 2. find its radius ?
Options: ['a. 8', 'b. 3', 'c. 4', 'd. 9', 'e. 7']

Answer:
c