A company making ceramic coffee cups finds that it can sell x cups per week at p dollars each, according to the formula p(x) = 40 − 0.2x. If the total cost to produce and sell x coffee cups is
C(x) = 3x + 40, and the revenue function R(x) = x · p(x) is given by the number of cups sold times the
price per cup, find and simplify the profit function, P(x) = R(x) − C(x).