Which of the following statements describes the main idea behind Keynes's aggregate expenditures model?
a) The demand for labor and the level of production depend on the level of expenditure in an economy.
b) When the level of output is high, prices will increase, reducing aggregate expenditures.
c) The demand for labor depends primarily on how much a given good or service can be sold for.
d) The prices of goods and services change rapidly when an economy enters and exits a recession.