13. A café's annual income depends on x, the number of customers. The function I(x) = 4x2 - 20x describes the café's total annual income. The function C(x) = 2x2 + 5 describes the total amount the café spends in a year. The café's annual profit, P(x), is the difference between the annual income and the amount spent in a year. Which function describes P(x)?​