upward-sloping national supply curve

Consider a two-country world. Each country has an upward-sloping national supply curve for raisins and a downward-sloping national demand curve for raisins. With no trade in raisins, the no-trade equilibrium price for raisins in one country would be $2.00 per kilogram and the no-trade equilibrium price for raisins in the other country would be $3.20 per kilogram. If the countries allow free trade in raisins, explain why $3.50 per kilogram cannot be the free-trade equilibrium world price for raisins. In your answer, draw and refer to graphs of supply and demand curves for the two national markets.