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: micheal and adam can do together a piece of work in 20 days. after they have worked together for 15 days micheal stops and adam completes the remaining work in 10 days. in how many days micheal complete the work separately.
Options: a. 40 days, b. 100 days, c. 120 days, d. 110 days, e. 90 days
[A]: a

[Q]: Problem: sheila works 8 hours per day on monday, wednesday and friday, and 6 hours per day on tuesday and thursday. she does not work on saturday and sunday. she earns $ 360 per week. how much does she earn in dollars per hour ?
Options: a. 11, b. 10, c. 9, d. 8, e. 7
[A]: b

[Q]: Problem: sally has a gold credit card with a certain spending limit, and a platinum card with twice the spending limit of the gold card. currently, she has a balance on her gold card that is 1 / 3 of the spending limit on that card, and she has a balance on her platinum card that is 1 / 7 of the spending limit on that card. if sally transfers the entire balance on her gold card to her platinum card, what portion of her limit on the platinum card will remain unspent ?
Options: a. 11 / 30, b. 29 / 42, c. 17 / 30, d. 19 / 30, e. 11 / 15
[A]:
b