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: 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.

Ex Output:
a


Ex Input:
Problem: a rope of which a calf is tied is increased from 12 m to 23 m, how much additional grassy ground shall it graze ?
Options: a. 2989, b. 2789, c. 1210, d. 1288, e. 1211

Ex Output:
c


Ex Input:
Problem: a sum of 14,800 amounts to 19,800 in 3 years at the rate of simple interest. what is the rate of interest ?
Options: a. 12 %, b. 11 %, c. 16 %, d. 15 %, e. 18 %

Ex Output:

b