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: a ( 3, w ^ 3 ) is the ( x, y ) coordinate of point located on the parabola y = x ^ 2 - 1. what is the value of w ?
Options: a. 2., b. 4., c. 5., d. 6., e. 9.
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 49 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. 105, b. 120, c. 140, d. 147, e. 168
Example Output: a

Example Input: Problem: a rectangular garden is to be twice as long as it is wide. if 180 yards of fencing, including the gate, will completely enclose the garden, what will be the length of the garden, in yards ?
Options: a. 60, b. 70, c. 80, d. 90, e. 100
Example Output:
a