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.

Input: Consider Input: Problem: a, b, c can complete a piece of work in 24, 8,12 days. working together, they complete the same work in how many days ?
Options: a. 4, b. 4 / 5, c. 7 / 9, d. 10, e. 24 / 7

Output: a

Input: Consider Input: Problem: the average runs scored by a batsman in 30 matches is 50. in the next 15 matches the batsman scored an average of 26 runs. find his average in all the 45 matches ?
Options: a. 31, b. 42, c. 29, d. 97, e. 27

Output: b

Input: Consider Input: Problem: if x is an integer and 2.134 10 ^ x is less than 21,000, what is the greatest possible value for x ?
Options: a. 7, b. 6, c. 5, d. 4, e. 3
Output: e