A Manufacturer Finds That the Revenue Generated by Selling X $R ( x ) = 80 x - 0.2 x ^ { 2 }$

A manufacturer finds that the revenue generated by selling x units of a certain commodity is given by the function, $R ( x ) = 80 x - 0.2 x ^ { 2 }$ where the revenue $R ( x )$
Is measured in dollars. What is the maximum revenue, and how many units should be manufactured to obtain this maximum?

A) Maximum Revenue: $\$ 8,000$
When $x = 2000$
Units are manufactured
B) Maximum Revenue: $\$ 8,000$
When $x = 100$
Units are manufactured
C) Maximum Revenue: $\$ 8,500$
When $x = 250$
Units are manufactured
D) Maximum Revenue: $\$ 9,000$
When $x = 200$
Units are manufactured
E) none of these