The Demand for Shoes in a Country Is Given by D

The demand for shoes in a country is given by D = 60 - 0.5P,where P is the price of a pair of shoes.Supply by domestic producers is given by S = 20 + 0.5P.The world price of a pair of shoes equals $30.In equilibrium,when this economy is closed to trade,the quantity of shoes demanded domestically equals _________,and when this economy opens to trade,the quantity of shoes demanded domestically equals _________.

A) 40;35
B) 40;45
C) 35;40
D) 45;40
E) 45;35