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.

[EX Q]: Problem: the population of a town increases 25 % and 40 % respectively in two consecutive years. after the growth the present population of the town is 1750. then what is the population of the town 2 years ago ?
Options: a. a. 750, b. b. 800, c. c. 850, d. d. 900, e. e. 950
[EX A]: b

[EX Q]: Problem: raman mixed 48 kg of butter at rs. 150 per kg with 36 kg butter at the rate of rs. 125 per kg. at what price per kg should he sell the mixture to make a profit of 40 % in the transaction ?
Options: a. 129, b. 287, c. 195, d. 188, e. 112
[EX A]: c

[EX Q]: Problem: bill downloads the movierevenge of the avengersto his computer in 2.5 hours, using a download manager that downloads from 3 sources marked a, b and c. each source provides download at a constant rate, but the rates of different sources are not necessarily identical. if the movie was downloaded from sources a and c alone, it would take 4 hours to complete the download. the next day, source b is available, but the other sources are inactive. how long will it take to download the trailer of the movie, a file that is 10 times smaller, from source b alone ?
Options: a. 40 minutes, b. 15 minutes, c. 12 minutes, d. 10 minutes, e. 3 minutes
[EX A]:
a