# Calculus: Other Calculus Problems – #500

Question: Suppose that when its $$x$$ years old, an industrial machine generates revenue at the rate of $$R(x)=5920-12{{x}^{2}}$$ per year, and results in costs that accumulate at the rate of $$C(x)=4000+18{{x}^{2}}$$

a) For how many years is the use of the machine profitable?

b) Find the net earnings generated by the machine during the time it’s profitable.