Answer
p=15 will produce the highest total sales (7200).
Work Step by Step
$S=-32p^{2}+960p$
In order to find the height of the parabola, use the equation $\frac{-b}{2a}$
$h=\frac{-b}{2a}=\frac{-960}{2(-32)}=15$
Thus, $p=15$ will produce the highest total sales (7200).
