Transcript text: $C$ and $D$ are sets of real numbers defined as follows.
\[
\begin{array}{l}
C=\{z \mid z \geq 4\} \\
D=\{z \mid z>5\}
\end{array}
\]
Write $C \cap D$ and $C \cup D$ using interval notation. If the set is empty, write $\varnothing$.
\[
C \cap D=
\]
$\square$
\[
C \cup D=
\]
$\square$