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, b, c can complete a piece of work in 24, 8,12 days. working together, they complete the same work in how many days ?
Options: a. 4, b. 4 / 5, c. 7 / 9, d. 10, e. 24 / 7

A: a
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Q: Problem: how many multiples of 4 are there between 12 and 104, inclusive ?
Options: a. 21, b. 22, c. 23, d. 24, e. 25

A: d
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Q: Problem: a person crosses a 1080 m long street in 12 minutes. what is his speed in km per hour ?
Options: a. 4.1, b. 4.5, c. 4.8, d. 5.4, e. 5.5

A:
d
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