5 The nation of Textilia does not allow imports of clothing. In its equilibrium without trade, a T-shirt costs $20, and the equilibrium quantity is three mil lion T-shirts. One day, after reading Adam Smith's The Wealth of Nations while on vacation, the president decides to open the Textilian market to international trade. The market price of a T-shirt falls to the world price of $16. The number of T-shirts consumed in Textilia rises to four million, while the number of T-shirts produced declines to one million.

a Illustrate the situation just described in a graph. Your graph should show all the numbers.

b Calculate the change in consumer surplus, producer surplus and total surplus that results from opening up trade. (Hint: Recall that the area of a triangle is½ x base x height.)