7. (10 points) There are three locations $A$, $O$, and $B$ on a road, with $O$ between $A$ and $B$. The distance between $A$ and $O$ is 1620 meters. Two people, A and B, start from $A$ and $O$ respectively at the same time and head towards $B$. After 12 minutes, the distances of A and B from $O$ are equal; after 36 minutes, A and B meet at $B$. What is the distance between $O$ and $B$ in meters? $\qquad$ meters.