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 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

[Q]: Problem: when positive integer n is divided by 3, the remainder is 1. when n is divided by 7, the remainder is 5. what is the smallest positive integer k such that k + n is a multiple of 21 ?
Options: a. 2, b. 4, c. 6, d. 8, e. 10
[A]: a

[Q]: Problem: there is food for 760 men for 22 days. how many more men should join after two days so that the same food may last for 5 days more ?
Options: a. 2280, b. 2240, c. 2299, d. 2288, e. 2266
[A]:
a