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: 3 candidates in an election and received 6136, 7636 and 11628 votes respectively. what % of the total votes did the winning candidate got in that election ?
Options: a. 46 %, b. 49 %, c. 57 %, d. 59 %, e. 61 %
Example Output: a

Example Input: Problem: car x began traveling at an average speed of 35 miles per hour. after 72 minutes, car y began traveling at an average speed of 70 miles per hour. when both cars had traveled the same distance, both cars stopped. how many miles did car x travel from the time car y began traveling until both cars stopped ?
Options: a. 15, b. 20, c. 40, d. 42, e. 68
Example Output: d

Example Input: Problem: a bottle contains a certain solution. in the bottled solution, the ratio of water to soap is 3: 2, and the ratio of soap to salt is two times this ratio. the solution is poured into an open container, and after some time, the ratio of water to soap in the open container is halved by water evaporation. at that time, what is the ratio of water to salt in the solution ?
Options: a. 1: 1, b. 2: 3, c. 3: 2, d. 9: 4, e. 18: 8
Example Output:
e