Tiffany and her husband were legally divorced in $2017.$ After the divorce, Tiffany retained physical custody of their children. Tiffany received the following amounts from her ex$-$husband, on behalf of the children or as ordered by the court through a divorce decree:

Court$-$ordered child support of $$2,000$ per month.

Court$-$ordered alimony of $$1,000$ per month.

How much of this income is taxable and must be reported on her federal return?

$$0$

$$12,000$

$$24,000$

$$36,000$