a)

Demand function is given as follows:

 

Supply function is given as follows:

 

With free trade an international price is $60 per barrel.

By substituting price of $60 per barrel in the equation (1) and (2), find the quantity demand, and quantity supply.

 

Thus, the quantity demand is 5.3 with international trade.

 

Thus, the quantity supply is 2.0 with international trade.
 
 
 

P=325-50.Q...(1)