Final answer:
The expenditure multiplier is 20 in the given equation AE = 800 + .95Y.
Step-by-step explanation:
The expenditure multiplier measures the change in equilibrium output resulting from a change in autonomous expenditure. It is calculated as: expenditure multiplier = 1 / (1 - marginal propensity to consume).
In the given equation AE = 800 + .95Y, the marginal propensity to consume is 0.95. Therefore, the expenditure multiplier would be 1 / (1 - 0.95) = 20.
So, the correct answer is a. 20.