Task: Question Answering
Input (English): 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
Output (English): b