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: buses a and b start from a common bus stop x. bus a begins to travel in a straight line away from bus b at a constant rate of 30 miles per hour. one hour later, bus b begins to travel in a straight line in the exact opposite direction at a constant rate of 50 miles per hour. if both buses travel indefinitely, what is the positive difference, in minutes, between the amount of time it takes bus b to cover the exact distance that bus a has covered and the amount of time it takes bus b to cover twice the distance that bus a has covered ?
Options: a. 36, b. 84, c. 132, d. 144, e. 180
[EX A]: b

[EX Q]: Problem: virginia, adrienne, and dennis have taught history for a combined total of 96 years. if virginia has taught for 9 more years than adrienne and for 12 fewer years than dennis, for how many years has dennis taught ?
Options: a. 23, b. 32, c. 35, d. 41, e. 42
[EX A]: e

[EX Q]: Problem: a worker is paid a regular rate of rs. 10 for completing a survey. the worker completes 50 surveys per week. for any survey involving the use of her cellphone, she is paid at a rate of that is 30 % higher than her regular rate. if she completed 35 surveys involving the use of her cellphone, how much did she get that week ?
Options: a. 605, b. 505, c. 105, d. 100, e. 200
[EX A]:
a