Chapter 4 - Polynomials - 4.3 Polynomials - 4.3 Exercise Set - Page 253: 85

$$2510$$

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 30 monitors is: $$-1.1\cdot \:30^2+250\cdot \:30-4000\\ 2510$$