A company that sells phones generates revenue given by the function
r(x) = x^2 + 20x + 50 (where x is the number of phones produced per month). The cost of production is given by the function c(x) = 50x + 30. Which function gives the profit earned by the company?
x^2 + 70x + 80
x^2 + 70x + 20
x^2 – 30x + 20
x^2 + 30x + 20