For each of the following trade relationships, explain the likely source of the comparative advantage of each

Question:

For each of the following trade relationships, explain the likely source of the comparative advantage of each of the exporting countries.
a. The United States exports software to Venezuela, and Venezuela exports oil to the United States.
b. The United States exports airplanes to China, and China exports clothing to the United States.
c. The United States exports wheat to Colombia, and Colombia exports coffee to the United States.