Step-by-step explanation:
Italy's opportunity cost of producing a pound of cheese is
= 5 barrels of beer
Germany's opportunity cost of producing a pound of cheese is
= 10 barrels of beer
Italy's opportunity cost of producing a barrel of beer is
=

= 0.2 pounds of cheese
Germany's opportunity cost of producing a barrel of beer is
=

= 0.1 pounds of cheese
Italy has a comparative advantage in producing cheese, while Germany has a comparative advantage in producing beer.
A country is said to be enjoying a comparative advantage if it can produce a good at a lower opportunity cost.
Italy can gain from trade if it is getting more than 5 barrels of beer for each pound of cheese. Similarly, Germany can gain from trade if it is getting more than 0.1 pounds of cheese.
Both the countries will gain from the trade if the price of trade is 8 barrels of beer per pound of cheese and 9 barrels of beer per pound of cheese.
Italy will not accept 3 barrels of beer per pound of cheese and 1 barrel of beer per pound of cheese because it is not covering the opportunity cost.