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: if jack walked 8 miles in 1 hour and 15 minutes, what was his rate of walking in miles per hour ?
Options: a. 4, b. 4.5, c. 6, d. 6.4, e. 15

A: d
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Q: Problem: the population of a town increases 25 % and 40 % respectively in two consecutive years. after the growth the present population of the town is 1750. then what is the population of the town 2 years ago ?
Options: a. a. 750, b. b. 800, c. c. 850, d. d. 900, e. e. 950

A: b
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Q: Problem: ( p / q - q / p ) = 21 / 10. then find 4 p / q + 4 q / p ?
Options: a. 58 / 9, b. 58 / 5, c. 58 / 7, d. 58 / 2, e. 58 / 1

A:
b
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