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 can give b 100 meters start and c 200 meters start in a kilometer race. how much start can b give c in a kilometer race ?
Options: a. 111.12 m, b. 221.12 m, c. 271.12 m, d. 611.12 m, e. 191.12 m

A: a
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Q: Problem: by selling 15 pencils for a rupee a man loses 20 %. how many for a rupee should he sell in order to gain 20 % ?
Options: a. 8, b. 7, c. 6, d. 4, e. 10

A: e
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Q: Problem: by selling 100 pens, a trader gains the cost of 30 pens. find his gain percentage ?
Options: a. 30 %, b. 33 %, c. 31 %, d. 32 %, e. 34 %

A:
a
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