Answer: The theory of comparative advantage
Step-by-step explanation:
When a country is able to produce certain goods or service at a lower cost (known as an opportunity cost) compared to another country this is known as comparative advantage.
This lower cost or opportunity cost is what will be used to determine a trade between countries.
The country may not be doing well at producing that product but the fact that they are able to produce those products at a lower cost they will always benefits greatly from the trade off.