If the opportunity cost of corn to wheat is 3:1 in the United States and 5:1 in France, only the United States would benefit from trade if the actual terms of trade between corn and wheat were 2:1.

Both countries can benefit from trade if the terms of trade are between their respective opportunity costs. Since the actual terms of trade (2:1) are between the U.S. opportunity cost (3:1) and France's opportunity cost (5:1), both countries can specialize in the production of the good for which they have a comparative advantage and trade based on these terms, thereby gaining from trade.