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.

Example Input: Problem: if jack walked 8 miles in 1 hour and 15 minutes, what was his rate of walking in miles per hour ?
Options: a. 4, b. 4.5, c. 6, d. 6.4, e. 15
Example Output: d

Example Input: Problem: last year elaine spent 20 % of her annual earnings on rent. this year she earned 35 % 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. 202.5, b. 194.5, c. 197.5, d. 182.5, e. 177.5
Example Output: a

Example Input: Problem: the ratio of the number of red cars in a certain parking lot to the number of black cars is 3 to 8. if there are 90 black cars in the lot, how many red cars are there in the lot ?
Options: a. 11, b. 33, c. 24, d. 27, e. 32
Example Output:
b