Final answer:
A country can produce more of good X by reallocating resources along its production possibilities frontier towards the production of X, particularly shifting towards the good for which it has comparative advantage, leading to increased overall production.
Step-by-step explanation:
If a country is currently producing at point B and wants to produce more of good X, it can do so by reallocating resources and moving along its production possibilities frontier (PPF) to a different point that allows for greater production of X. In the context of the scenario where the United States and Mexico are shifting their production toward goods for which they have a comparative advantage, the U.S. moves labor from shoe production to refrigerator production. Consequentially, the U.S. sees a decrease in shoe production by 1,500 units but experiences an increase in refrigerator production by 6,000 units. Similarly, Mexico's shift towards more shoe production and less refrigerator production results in an increase of 2,000 pairs of shoes and a decrease of 2,500 refrigerators. These moves towards comparative advantage lead to an overall increase in combined production of both goods.