The mundelfleming model takes the world interst rate r* as anexogenous variable.Let,consider what happen when this variable changes.a,what maight cause the world interest rate torise? b,Inthe mundel fleming model with flaoting exchange rate,what happen to aggregate,the exchange rate,and trade balance when the word interst rate rises? c,In the mundel fleming model with fixed exchange rate,what happens to aggregate incom,the exchange rate,and trade balance when the world interet rate rises?