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: the average score of a cricketer in 2 matches is 30 and in other 3 matches is 40. then find the average score in all the 5 matches ?
Options: a. 25, b. 27, c. 30, d. 35, e. 36
[A]: e


[Q]: Problem: a movie buff buys movies on dvd and on blu - ray in a ratio of 13: 4. if she returns 2 blu - ray movies, that ratio would change to 7: 2. if she buys movies on no other medium, what was the original number of movies purchased ?
Options: a. 22, b. 28, c. 77, d. 99, e. 119
[A]: e


[Q]: Problem: three pipes, a, b, & c are attached to a tank. a & b can fill it in 20 & 30 minutes respectively while c can empty it in 20 minutes. if a, b & c are kept open successively for 1 minute each, how soon will the tank be filled ?
Options: a. 2 hours, b. 4 hours, c. 1 hour 30 min, d. 5 hours, e. 6 hours
[A]:
c