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: two trains, one from howrah to patna and the other from patna to howrah, start simultaneously. after they meet, the trains reach their destinations after 10 hours and 8 hours respectively. the ratio of their speeds is
Options: a. 4: 9, b. 4: 3, c. 4: 12, d. 4: 8, e. 4: 5

A: e
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Q: Problem: if julie rows 32 km upstream and 72 km down steam taking 4 hours each, then the speed of the stream
Options: a. 1.5 kmph, b. 0.5 kmph, c. 0.4 kmph, d. 1.6 kmph, e. 2.5 kmph

A: b
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Q: Problem: on a certain day, tim invested $ 600 at 10 percent annual interest, compounded annually, and lana invested 800 at 5 percent annual interest, compounded annually. the total amount of interest earned by tim ’ s investment in the first 2 years was how much greater than the total amount of interest earned by lana ’ s investment in the first 2 years ?
Options: a. $ 5, b. $ 15, c. $ 44, d. $ 100, e. $ 105

A:
c
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