In macroeconomics, when a price is constant, equilibrium is achieved at a point where?

Option 1 -> This is a microeconomic equilibrium condition where price adjusts to clear the market, not applicable to macroeconomic equilibrium with constant prices.

Option 2 -> Ex-post values are actual/realized values. Ex-post AD always equals AS by accounting identity, regardless of whether equilibrium exists.

Option 3 -> Ex ante values are planned/intended values. In macroeconomic equilibrium with constant prices (Keynesian framework), equilibrium occurs when planned aggregate demand equals planned aggregate supply.

Option 4 -> This is incorrect. Equilibrium does not require consumption to equal investment. In equilibrium, Y = C + I (in a simple model), not C = I.

Hence, Option 3: Ex ante Aggregate Demand = Ex ante Aggregate Supply -> In macroeconomics, particularly in Keynesian models where prices are sticky or constant, equilibrium is achieved when planned (ex ante) aggregate demand equals planned (ex ante) aggregate supply. This is distinct from ex-post equality which always holds as an accounting identity. When ex ante AD ≠ ex ante AS, unplanned inventory changes occur, pushing the economy toward equilibrium where planned spending equals planned output -> correct