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.

Q: Problem: a train running at the speed of 20 km / hr crosses a post in 10 seconds. what is the length of the train ?
Options: a. 150, b. 250, c. 415, d. 200, e. 312

A: d
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Q: Problem: what least number must be subtracted from 13294 so that the remainder is exactly divisible by 97 ?
Options: a. 3, b. 5, c. 7, d. 9, e. 10

A: b
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Q: Problem: a sports retailer ordered white and yellow tennis balls in equal number but the dispatch clerk of the tennis ball company erred and dispatched 50 extra yellow balls and making ratio of white balls to yellow balls 8 / 15. how many tennis balls did the retailer order originally.
Options: a. 110, b. 114.28, c. 140, d. 160, e. 214

A:
b
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