5. Explain why the following statements are false:

a. ‘The aggregate demand curve slopes downward because it is the horizontal sum of the demand curves for individual goods.’

b. ‘The long-run aggregate supply curve is vertical because economic forces do not affect long-run aggregate supply.’

c. ‘If firms adjusted their prices every day, then the shortrun aggregate supply curve would be horizontal.’

d. ‘Whenever the economy enters a recession, its long-run aggregate supply curve shifts to the left.’