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.
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Question: Problem: a waitress ' s income consists of her salary and tips. during one week, her tips were 3 / 4 of her salary. what fraction of her income for the week came from tips ?
Options: a. 1 / 9, b. 1 / 6, c. 3 / 7, d. 4 / 9, e. 5 / 9

Answer: c

Question: Problem: if a person walks at 25 km / hr instead of 10 km / hr, he would have walked 20 km more. the actual distance traveled by him is :
Options: a. 50 km, b. 56 km, c. 13.3 km, d. 70 km, e. 80 km

Answer: c

Question: Problem: the area of sector of a circle whose radius is 12 metro and whose angle at the center is 30 is ?
Options: ['a. 35 m 2', 'b. 36 m 2', 'c. 37 m 2', 'd. 38 m 2', 'e. 40 m 2']

Answer:
c