Solve the Problem $$x = - 6 p + 120 , \quad 0 \leq p \leq 20$$

Multiple Choice

Solve the problem.
-The price p (in dollars) and the quantity x sold of a certain product obey the demand equation $$x = - 6 p + 120 , \quad 0 \leq p \leq 20$$ What quantity x maximizes revenue? What is the maximum revenue?

A) 60; $600
B) 90; $450
C) 30; $450
D) 120; $600