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: if n = 2 ^ 0.15 and n ^ b = 1, b must equal
Options: a. 3 / 80, b. 20 / 3, c. 4, d. 5 / 3, e. 80 / 3

Answer: b


Question: Problem: how many positive even integers less than 100 contain digits 5 or 7 ?
Options: a. 10, b. 17, c. 18, d. 19, e. 20

Answer: a


Question: Problem: two ships are sailing in the sea on the two sides of a lighthouse. the angle of elevation of the top of the lighthouse is observed from the ships are 30 º and 45 º respectively. if the lighthouse is 100 m high, the distance between the two ships is :
Options: a. 173 m, b. 200 m, c. 273 m, d. 300 m, e. none of these

Answer:
c