Please assist with the given problems.
Task: Consider the same setup as previous questions, but instead of introducing free trade (free movement of goods and services), we introduce free mobility of skilled and unskilled labor.
Question 1: In what direction will unskilled labor migrate? What about skilled labor? Why?
Question 2: When would skilled and unskilled labor stop migrating across borders?
Question 3: At that point, would it still pay off to introduce free trade? Why or why not?
Question 4: "Free trade is a substitute for the mobility of factors of production." Explain.