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 Input:
Problem: last year elaine spent 20 % of her annual earnings on rent. this year she earned 20 % more than last year and she spent 30 % of her annual earnings on rent. the amount she spent on rent this year is what percent of the amount spent on rent last year ?
Options: a. 185.5, b. 180.0, c. 167.5, d. 172.5, e. 177.5

Ex Output:
b


Ex Input:
Problem: aaron will jog from home at 2 miles per hour and then walk back home by the same route at 4 miles per hour. how many miles from home can aaron jog so that he spends a total of 3 hours jogging and walking ?
Options: a. 5, b. 7, c. 3, d. 9, e. 10

Ex Output:
c


Ex Input:
Problem: a and b can together finish a work in 40 days. they worked together for 10 days and then b left. after another 21 days, a finished the remaining work. in how many days a alone can finish the job ?
Options: a. 10, b. 25, c. 60, d. 30, e. 28

Ex Output:

e