15. A number of professional associations, such as the American Medical Association and the American Bar Association, support regulations that make it more costly for their members (for example, doctors and lawyers) to practice their services. While some of these regulations may stem from a genuine desire for higherquality medical and legal services, self-interest may also play a role. Explain

18. Argyle is a large, vertically integrated firm that manufactures sweaters from a rare type of wool produced on its sheep farms. Argyle has adopted a strategy of selling wool to companies that compete against it in the market for sweaters. Explain why this strategy may, in fact, be rational. Also, identify at least two other strategies that might permit Argyle to earn higher profits