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: 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
[A]: b


[Q]: Problem: a fraudulent dairy guy declares to market his dairy at price range but he combined it with water and therefore benefits 25 %. the percentage of water in the combination is :
Options: a. 20 %, b. 30 %, c. 50 %, d. 35 %, e. 60 %
[A]: a


[Q]: Problem: a survey was sent to 65 customers, 7 of whom responded. then the survey was redesigned and sent to another 63 customers, 9 of whom responded. by approximately what percent did the response rate increase from the original survey to the redesigned survey ?
Options: a. 2 %, b. 4 %, c. 14 %, d. 28 %, e. 63 %
[A]:
b