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 train traveled the first d miles of its journey it an average speed of 50 miles per hour, the next d miles of its journey at an average speed of y miles per hour, and the final d miles of its journey at an average speed of 160 miles per hour. if the train ’ s average speed over the total distance was 96 miles per hour, what is the value of y ?
Options: a. 68, b. 84, c. 90, d. 120, e. 160
[EX A]: e

[EX Q]: Problem: the sector of a circle has radius of 24 cm and central angle 135 o. find its perimeter ?
Options: a. 91.5 cm, b. 11.5 cm, c. 104.6 cm, d. 92.5 cm, e. 99.5 cm
[EX A]: c

[EX Q]: Problem: marcella has 24 pairs of shoes. if she loses 9 individual shoes, what is the greatest number of matching pairs she could have left ?
Options: a. 21, b. 20, c. 19, d. 16, e. 15
[EX A]:
c