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: a certain sum is invested at simple interest at 18 % p. a. for two years instead of investing at 12 % p. a. for the same time period. therefore the interest received is more by rs. 300. find the sum ?
Options: a. 7000, b. 2500, c. 2778, d. 2800, e. 2791

A: b
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Q: Problem: a farmer spent $ 35 on feed for chickens and goats. he spent 40 % money on chicken feed, which he bought at a 50 % discount off the full price, and spent the rest on goat feed, which he bought at full price. if the farmer had paid full price for both the chicken feed and the goat feed, what amount would he have spent on the chicken feed and goat feed combined ?
Options: a. $ 37.80, b. $ 49, c. $ 39.20, d. $ 39.50, e. $ 40.60

A: b
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Q: Problem: the circulation for magazine p in 1961 was 4 times the average ( arithmetic mean ) yearly circulation for magazine p for the years 1962 - 1970. what is the ratio of the circulation in 1961 to the total circulation during 1961 - 1970 for magazine p ?
Options: a. 2 / 7, b. 5 / 7, c. 3 / 7, d. 4 / 7, e. 1 / 7

A:
a
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