One of the tools or models economists use is the production possibilities frontier. Using the production possibilities frontier:

• Explain the law of increasing opportunity cost and its relationship to the shape of the production possibilities frontier 
• Using the concept of comparative advantage and the production possibilities frontier explain why nations trade even when they could produce the product on their own
• Explain what would happen to the USA's production possibilities frontier if all illegal immigrants holding jobs in the USA were deported.

(current textbook is macro econ 5, work must be cited)