Answer
560
Work Step by Step
We first simplify the equation using the fact that revenue minus cost equals profit:
$$250x-0.5x^2-4000-0.6x^2 \\ -1.1x^2+250x-4000$$
Thus, we find that the profit for 20 monitors is:
$$250\cdot \:20-0.5\cdot \:20^2-\left(4000+0.6\cdot \:20^2\right) \\ 560$$