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 of 25 carriages, each of 60 meters length, when an engine also of 60 meters length is running at a speed of 60 kmph. in what time will the train cross a bridge 1.0 km long ?
Options: a. 2.5, b. 3, c. 5, d. 7, e. 9

A: a
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Q: Problem: subtracting 3 % of a from a is equivalent to multiplying a by how much ?
Options: a. 0.97, b. 9.4, c. 0.094, d. 94, e. none

A: a
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Q: Problem: 13 buckets of water fill a tank when the capacity of each bucket is 51 litres. how many buckets will be needed to fill the same tank, if the capacity of each bucket is 17 litres ?
Options: a. 39, b. 28, c. 23, d. 12, e. 24

A:
a
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