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: excluding the stoppages, the speed of a bus is 48 km / hr and including the stoppages the speed of the bus is 12 km / hr. for how many minutes does the bus stop per hour ?
Options: a. 45 min, b. 10 min, c. 12 min, d. 20 min, e. 18 min

A: a
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Q: Problem: evaluate: 98612 / 22 * 11 * 70 = ?
Options: a. 700.4, b. 704.4, c. 740.4, d. 744.4, e. 700.0

A: b
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Q: Problem: find the ratio in which rice at rs. 7.10 a kg be mixed with rice at rs. 5.70 a kg to produce a mixture worth rs. 6.30 a kg ?
Options: a. 1: 3, b. 2: 3, c. 3: 4, d. 4: 5, e. none of these

A:
c
****