Final answer:
The student's question pertains to the opportunity cost in trade, which is a fundamental concept in Economics. To answer it, specific data on production costs and trade exchange rates between the goods in question (tomatoes and green beans) would be necessary.
Step-by-step explanation:
The question appears to be related to the concept of opportunity cost and trade-offs in the field of Economics. Specifically, the student is asking about the amount of tomatoes or green beans that France would need to give up to gain from trade.
In economics, when a country decides to specialize in the production of one good over another, the opportunity cost is the amount of the other good that must be given up. This is a central concept in the study of trade and the potential benefits of specializing and engaging in trade with other countries.
To determine exactly how much France would have to give up in terms of tomatoes to gain from trade in green beans (or vice versa), one would need to know the relative costs of production and the trade exchange rates between tomatoes and green beans.
This information would provide the basis for calculating the opportunity cost and thus determine how much of one good France would need to forgo to acquire a unit of the other good.