21.What would happen to revenues if a firm in a perfectly competitive industry raised prices? A.They would increase B.They would increase but profit would decrease C.They would increase along with profit D.They would fall to zero 22.Managers undertake an investment only if A.Marginal benefits of the investment are greater than zero B.MCs of the investment are greater than marginal benefits of the investment C.Marginal benefits are greater than MCs D.Investment decisions do not depend on marginal analysis