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: 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.

Ex Output:
c

Ex Input:
Problem: find large number from below question the difference of two numbers is 1000. on dividing the larger number by the smaller, we get 10 as quotient and the 10 as remainder
Options: a. 1234, b. 1110, c. 1456, d. 1200, e. 1600

Ex Output:
b

Ex Input:
Problem: marginal cost is the cost of increasing the quantity produced ( or purchased. by one unit. if the fixed cost for n products is $ 15,000 and the marginal cost is $ 200, and the total cost is $ 25,000, what is the value of n ?
Options: a. 30, b. 50, c. 60, d. 80, e. 100

Ex Output:
b