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.
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Question: Problem: the speed of the boat in still water in 12 kmph. it can travel downstream through 54 kms in 3 hrs. in what time would it cover the same distance upstream ?
Options: a. 8 hours, b. 6 hours, c. 4 hours, d. 5 hours, e. 9 hours

Answer: e

Question: Problem: a train traveling at 72 kmph crosses a platform in 33 seconds and a man standing on the platform in 18 seconds. what is the length of the platform in meters ?
Options: a. 240 meters, b. 360 meters, c. 420 meters, d. 300 meters, e. can not be determined

Answer: d

Question: Problem: what is the smallest integer that is multiple of 5, 7,9
Options: a. a. 70, b. b. 315, c. c. 200, d. d. 280, e. e. 140

Answer:
b