3. Suppose an economy is represented by the following equations.
Consumption function C = 200 + 0.8Yd
Planned investment I = 400
Government spending G = 600
Exports EX = 200
Imports IM = 0.1Yd
Autonomous Taxes T = 500
Marginal Tax Rate t=0.2
Planned aggregate expenditure AE = C + I + G + (EX - IM)

By using the above information calculate the equilibrium level of income for this economy and explain why fiscal policy becomes less effective in an open economy