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: what is the units digit of ( 3 ^ 13 ) ( 4 ^ 13 ) ?
Options: a. 2, b. 4, c. 6, d. 7, e. 8

A: a
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Q: Problem: during a pizza buffet where a eats more times 1.8 than b, and b eats 8 times less than c. find the leat number of times all the 3 has to eat
Options: a. 350, b. 260, c. 360, d. 380, e. 285

A:
c
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