Answer
Maximum revenue when $p={\$} 80$
$R={\$} 12,800.$
Work Step by Step
$q=-2p+320$
Revenue is $R=pq=-2p^{2}+320\mathrm{p}$.
The graph of R(p) is a parabola (that opens down).
$a=-2, b=320, c=0.$
Maximum revenue occurs at the vertex, when
$p=-\displaystyle \frac{b}{2a}=-\frac{320}{2(-2)}={\$} 80$
The corresponding revenue is
$R=-2(80)^{2}+320(80)={\$} 12,800$
