Let $C 1$ and $C 2$ be the centres of the circles $x^2+y^2-2 x-2 y-2=0$ and $x^2+y^2-6 x-6 y+14=0$ respectively. If $P$ and $Q$ are the points of intersection of these circles, then the area (in sq. units) of the quadrilateral $\mathrm{PC}_1 \mathrm{QC}_2$ is
