Solve the Problem $p$ And the Quantity $x$ Sold of a Certain Product Obey the Demand Equation

Multiple Choice

Solve the problem.
-The price $p$ and the quantity $x$ sold of a certain product obey the demand equation
$$p = - \frac { 1 } { 4 } x + 120,0 \leq x \leq 480 .$$
What price should the company charge to maximize revenue?

A) $\$ 72$
B) $\$ 90$
C) $\$ 60$
D) $\$ 30$