Answer:
Portugal has comparative advantage in producing olives.
Switzerland has comparative advantage in producing fish.
Portugal can gain from trade if it receives more than 3 pounds of fish per crate of olives.
Switzerland can gain from trade if it receives more than 1/11 of olives for each pound of fish.
d. 18 pounds of fish per crate of olives.
Explanation:
Switzerland and Portugal both countries can produce Olives and fish. One country has advantage in producing fish while other has advantage in producing olives. Both countries can gain from trade if they find a intermediary way so that both countries can be in win win situation. It is beneficial for Portugal if it trades with Switzerland if it receives more than 3 pounds of fish.