CEVAP:

the answer to this problem is aggregate demand or aggregate expenditure. Keynesian
economy argues that equilibrium level of income is realized at the level where aggregate demand equals aggregate supply. Since the economy’s shortterm
production capacity is difficult to change in the short-run, the effective factor that determines the short-run equilibrium level of income is aggregate demand. Aggregate demand is called effective aggregate demand, at the level where the aggregate demand is equal to the aggregate supply. Accordingly, the level of equilibrium income that emerges shows the level of actual employment in that economy.