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: each of the three people individually can complete a certain job in 3, 4, and 6 hours, respectively. what is the lowest fraction of the job that can be done in 1 hour by 2 of the people working together at their respective rates ?
Options: a. 1 / 3, b. 9 / 20, c. 8 / 15, d. 5 / 12, e. 2 / 3

A: d
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Q: Problem: if x and y are positive integers and 3 + x + y + xy = 17, what is the value of x + y ?
Options: a. 3, b. 5, c. 6, d. 8, e. 9

A: c
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Q: Problem: if it takes a tub 3 minutes to drain 6 / 7 of its content, how much more time will it take for the tub to be empty ?
Options: a. 30 seconds, b. 1 minute, 12 seconds, c. 1 minute, 50 seconds, d. 2 minutes, 14 seconds, e. 4 minutes, 12 seconds

A:
a
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