$A B C$ plc is about to launch a new product. Facilities will allow the company to produce up to 20 units per week. The marketing department has estimated that at a price of $\$ 8,000$ no units will be sold, but for each $\$ 150$ reduction in price one additional unit per week will be sold.

Fixed costs associated with manufacture are expected to be $\$ 12,000$ per week.

Variable costs are expected to be $\$ 4,000$ per unit for each of the first 10 units; thereafter each unit will cost $\$ 400$ more than the preceding one. The most profitable level of output per week for the new product is:

A. 10 units 

B. 11 units 

C. 13 units 

D. 14 units 

E. 20 units