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: the ratio of the volumes of two cubes is 1331: 2197. what is the ratio of their total surface areas ?
Options: a. 121: 169, b. 169: 122, c. 81: 124, d. 81: 126, e. 81: 129

Answer: a


Question: Problem: a train of length 250 m crosses a bridge of length 150 m in 20 seconds. what is the speed of train ?
Options: a. 33, b. 27, c. 25, d. 22, e. 72

Answer: e


Question: Problem: if x is invested in a bank at a rate of simple interest of y % p. a. for two years, then the interest earned is 900. if x is invested at y % p. a., for two years when the interest is compounded annually, the interest is 922.50. what is the value of x ?
Options: a. 9000, b. 6000, c. 5000, d. 4000, e. 3000

Answer:
a