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: john left home and drove at the rate of 45 mph for 2 hours. he stopped for lunch then drove for another 3 hours at the rate of 45 mph to reach his destination. how many miles did john drive ?
Options: a. 235 miles., b. 245 miles., c. 225 miles., d. 265 miles., e. 275 miles.
Example Output: c

Example 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
Example Output: d

Example Input: Problem: if a is a positive integer, and if the units digit of a ^ 2 is 4 and the units digit of ( a + 1 ) ^ 2 is 1, what is the units digit of ( a + 2 ) ^ 2 ?
Options: a. 0, b. 2, c. 4, d. 6, e. 8
Example Output:
a