4. Assume that a rm produces Q = f (L) units of a commodity using L units of labor. The rm earns p dollars per unit sold and pays 0 dollars per unit of labor. The amount of labor that maximizes the prot is denoted by L* (assume this coincides with a stationary point of the prot function). How many of the statements below are true? 0 The prot function is 7r(L) = pf(L) c. o The marginal prot function is 71' (L) : pf' (L) c. u f'(L*) = 19). o The marginal cost is a constant function. a f"(L*) > 0