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: if n = 2 ^ 0.15 and n ^ b = 1, b must equal
Options: a. 3 / 80, b. 20 / 3, c. 4, d. 5 / 3, e. 80 / 3

Ex Output:
b

Ex Input:
Problem: if the simple interest on a certain amount in at 4 % rate 5 years amounted to rs. 2240 less than the principal. what was the principal ?
Options: a. 1500, b. 2500, c. 2507, d. 2800, e. 11500

Ex Output:
d

Ex Input:
Problem: sue ' s trail mix is 30 % nuts and 70 % dried fruit. jane ' s trail mix is 60 % nuts and 40 % chocolate chips. if the combined mixture of sue and jane ' s trails mix contains 40 % nuts, what percent of the combined mixture is dried fruit ?
Options: a. 16.7 %, b. 23.33 %, c. 25 %, d. 33.3 %, e. 46.7 %

Ex Output:
e