Answer:
b. In the first economy, the spending multiplier is greater than in the second economy. In the third economy, the spending multiplier is undefined
Step-by-step explanation:
This can be easily understood by going through some calculations in a spending multiplier formula.
WORKINGS
The formula for Spending Multiplier =

Spending Multiplier
Economy 1: Multiplier =
= 2
Economy 2: Multiplier =
= 1
Economy 3: Multiplier =
= undefined
Note: MPS can be abbreviated as Marginal propensity to save
As we can see here economy 1 is 50% greater than economy 2 and economy 3 is undefined because they spend whole dollar they earn additionally.
On behalf of the above calculations, option B is a perfect match!