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: 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
[EX A]: e

[EX Q]: Problem: in what time will a railway train 50 m long moving at the rate of 36 kmph pass a telegraph post on its way ?
Options: a. 5 sec, b. 4 sec, c. 3 sec, d. 6 sec, e. 1 sec
[EX A]: a

[EX Q]: Problem: a box contains 7 pairs of shoes ( 14 shoes in total ). if two shoes are selected at random, what it is the probability that they are matching shoes ?
Options: a. 1 / 190, b. 1 / 20, c. 1 / 19, d. 1 / 13, e. 1 / 9
[EX A]:
d