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.

Example Input: Problem: the mean of 50 observations is 200. but later he found that there is decrements of 34 from each observations. what is the the updated mean is ?
Options: a. 165, b. 166, c. 190, d. 198, e. 199
Example Output: b

Example Input: 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
Example Output: b

Example Input: Problem: x can finish a work in 25 days. y can finish the same work in 20 days. y worked for 12 days and left the job. how many days does x alone need to finish the remaining work ?
Options: a. 2, b. 5, c. 6, d. 7, e. 8
Example Output:
e