A company has determined that the price and the monthly demand of one of its products are related by the equation D = √(400 − p), where p is the price per unit in dollars and D is the monthly demand. The associated fixed costs are $1,125/month, and the variable costs are $100/unit. Use this information to answer Problems 2-52 and 2-53. Select the closest answer.

What is the optimal number of units that should be produced and sold each month?

(a) 10 units 

(b) 15 units 

(c) 20 units

(d) 25 units