Explain why the following statements are false.

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

b. ‘The LRAS curve is vertical because economic forces do not affect LRAS.’

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

d. ‘Whenever the economy enters a recession, its LRAS curve shifts to the left.’