Consider the model of aggregate demand in an open economy with imperfect capital mobility, floating exchange rate, static exchange rate expectations, and capital flow (CF) is defined as foreigners' purchases of domestic assets minus domestic residents' purchases of foreign assets. Hence, aggregate demand is determined by the system PM=L(i,Y),Y=E(Y,ie,G,T,PP),CF(ii)+NX(Y,ie,G,T,PP)=0. (a) Derive an expression for the slope of the goods-market curve. (b) What is the sign of this slope (expression)? Please state all additional assumptions in support of your answer..