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 20 typists can type 50 letters in 30 minutes, then how many letters will 40 typists working at the same rate complete in 1 hour ?
Options: a. 400, b. 500, c. 350, d. 250, e. 200

A: a
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Q: Problem: the sum of 4 consecutive even numbers is 140. what would be the smallest number ?
Options: a. 32, b. 88, c. 70, d. 123, e. 12

A: a
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Q: Problem: 39 persons can repair a road in 12 days, working 5 hours a day. in how many days will 30 persons, working 3 hours a day, complete the work ?
Options: a. 10, b. 26, c. 14, d. 15, e. 16

A:
b
****