1. If Crusoe currently catches 5.5 pounds of fish and picks 11 pounds of berries a day, what is his opportunity cost of an extra pound of berries? And what is his opportunity cost of an extra pound of fish?

Write your answers in complete sentences.

A: His opportunity cost of a pound of berries and a pound of fish are both zero.

The opportunity cost is zero because he is operating inside his production possibilities frontier. He could pick 4 more pounds of berries without giving up any fish or catch 2 more fish without giving up any berries.

Please explain, where did it come up with the numbers 4 pounds of berries and catching 2 more fish.