Answer: a. The money supply decrease would shift the AD to the left; the new investment tax credit would shift AD to the right.
Step-by-step explanation:
If the money supply is decreased, it means the amount of money available in the economy for people to buy goods and services will reduce. When this happens, people will demand less because they have less cash. This will end up pushing the demand curve to the left.
When an investment tax credit is declared however, companies will feel more inclined to invest in the economy because they will pay less tax. As they invest more, people will be employed and will increase their spending thereby pushing the AD curve to the right.