Answer
$500$ dollars.
$1,000,000$ dollars.
Work Step by Step
Step 1. Given $R(p)=-4p^2+4000p$, let $a=-4, b=4000$, we know that the maximum of $R(p)$ happens when $p=-\frac{b}{2a}=-\frac{4000}{2(-4)}=500$ dollars.
Step 2. The maximum revenue is $R(500)=-4(500)^2+4000(500)=1,000,000$ dollars.