Answer:
A) 3 bushels of wheat and 3 bushels of corn, and this point lies outside of Cliff's production possibilities frontier.
Explanation:
Paul's production possibilities frontier = 8 bushels of wheat ; 10 bushels of corn
Cliff's production possibilities frontier = 6 bushels of wheat ; 4 bushels of corn
Paul's opportunity cost of producing 1 bushel of corn = 8/10 = 4/5 bushels of wheat.
Cliff's opportunity cost of producing 1 bushel of wheat = 4/6 = 2/3 of corn
So Paul should specialize in producing corn with a total production of 10 bushels of corn and Cliff will specialize in producing wheat with a total production of 6 bushels of wheat.
If Cliff trades 3 bushels of wheat for 3 bushels of corn, he will be able to consume 3 bushels of wheat (= 6 - 3) and 3 bushels of corn, resulting in a net gain of 1.5 bushels of wheat.