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3. (15 pts) (a) Why is knowing the level of potential output important to designing appropriate fiscal policy? (b) Using Aggregate Demand and Supply curves, graphically illustrate a situation in which expansionary fiscal policy could be helpful to a national economy. Briefly explain. (c) Using Aggregate Demand and Supply curves, graphically illustrate a situation in which the same expansionary fiscal policy could be damaging to a national economy. Briefly explain