Final answer:
Comparative advantage allows countries to specialize in producing goods where they have a lower opportunity cost. By specializing and trading, both the United States and Mexico can increase their total production and consume more of both goods. However, the question does not provide enough information to determine the exact additional tons of hamburgers that can be produced.
Step-by-step explanation:
Comparative advantage is the ability of a country to produce a good at a lower opportunity cost than another country. In this scenario, the United States has a comparative advantage in producing refrigerators because it can produce 1,000 refrigerators with one worker, while Mexico requires four workers to produce the same quantity. On the other hand, Mexico has a comparative advantage in producing shoes because it can produce 6,000 pairs of shoes with its resources, compared to the United States' production of 3,500 pairs.
By specializing in the goods they have a comparative advantage in, both countries can increase their total production. If the United States focuses solely on producing refrigerators and Mexico focuses solely on producing shoes, they can produce more than if they tried to produce both goods on their own. The additional tons of hamburgers that can be produced when they specialize and trade depends on the resources that are freed up by focusing on their respective comparative advantages.
In this case, since the question does not provide information about the resources freed up by specializing, it is not possible to calculate the specific additional tons of hamburgers that can be produced.