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: water is leaking out from a cylinder container at the rate of 0.31 m ^ 3 per minute. after 10 minutes, the water level decreases 1 / 9 meters. what is value of the radius in meters ?
Options: a. 2, b. 3, c. 4, d. 6, e. 9

Answer: b


Question: Problem: find the value of 1 / ( 3 + 1 / ( 3 + 1 / ( 3 - 1 / 3 ) ) )
Options: a. 21 / 29, b. 27 / 89, c. 89 / 21, d. 29 / 21, e. none

Answer: b


Question: Problem: a group of 7 teenagers recently visited the japanese restaurant. the total bill for the meal, including 20 % gratuity, came to $ 840. on average, how much did the meal of each individual cost before gratuity ?
Options: a. $ 160, b. $ 96, c. $ 90, d. $ 10, e. $ 55

Answer:
d