If $A =[ 1/2 ,7/2]$ and $B = (1,9/2)$, show whether $A\cup B$ is compact or not.

Question

If $A =[ 1/2 ,7/2]$ and $B = (1,9/2)$, show whether $A \cup B$ is compact or not. Here $A$ is closed and $B$ is open set , but I not understand that whether $A \cup B$ is closed or open.