Duke and his wife were legally divorced in $2021.$ After the divorce, Duke retained physical custody of their son. Duke received the following amounts from his ex$-$wife, on behalf of their son 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 should be reported on Duke's federal return?

$$0$

$$12,000$

$$24,000$

$$36,000$