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 man ' s speed with the current is 18 km / hr and the speed of the current is 2.5 km / hr. the man ' s speed against the current is ?
Options: a. 10, b. 18, c. 50, d. 30, e. 40

Answer: b


Question: Problem: a merchant marks goods up by 80 % and then offers a discount on the marked price. the profit that the merchant makes after offering the discount is 35 %. what % discount did the merchant offer ?
Options: a. 20 %, b. 25 %, c. 30 %, d. 35 %, e. 40 %

Answer: b


Question: Problem: the ratio of a to b is 4 to 5, where a and b are positive. if x equals a increased by 25 percent of a, and m equals b decreased by 40 percent of b, what is the value of m / x ?
Options: a. 2 / 5, b. 3 / 4, c. 4 / 5, d. 5 / 4, e. 3 / 5

Answer:
e