1. A) It's said that trade creates wealth. If wealth is determined by the total value of goods and services (including environmental goods and leisure time) people have, explain why allowing people to specialize and trade will make them wealthier.

B) Are the costs incurred up to that point considered as sunk costs?

C) Suppose that the costs of continuing the trail cause the firm to stop the development of the drug. Are the costs of continuing the trial considered the sunk costs?