11. Determine the altitude of the triangle

$ABC$ and $PQR$ are similar triangles. If the lengths of $AB$ and $PQ$ are 7 $cm$ and 9 $cm$, respectively. The corresponding altitude of $\triangle ABC$ is 9 $cm$, then the corresponding altitude of $\triangle PQR$ is 13.57112.57110.57111.571 $cm$.