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: given that p is a positive even integer with a positive units digit, if the units digit of p ^ 3 minus the units digit of p ^ 2 is equal to 0, what is the units digit of p + 4 ?
Options: a. 7, b. 8, c. 10, d. 11, e. 12

A: c
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Q: Problem: if a - b = 6 and a 2 + b 2 = 50, find the value of ab.
Options: a. a. 7, b. b. 12, c. c. 15, d. d. 18, e. e. 20

A: a
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Q: Problem: the moon revolves around the earth at a speed of approximately 0.2 kilometers per second. this approximate speed is how many kilometers per hour ?
Options: a. 60, b. 720, c. 62.5, d. 3,600, e. 3,672

A:
b
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