a. Mary Jane has a comparative advantage in law so she should specialize in law and hire a carpenter to make her cabinets.
Mary Jane is a lawyer who can earn $150 per hour in her law practice. She is also an excellent carpenter who can build cabinets three times as fast as the best carpenter, whose hourly wage is $20 per hour.
d. Mary Jane is three times faster than any carpenter so she should give up her law practice to become a carpenter.
I. The opportunity cost of moving from point P to point R is 10 units of Y.