The figure shows a fixed circle $C_{1}$ with equation $(x-1)^{2}+y^{2}=1$ and a shrinking circle $C_{2}$ with radius $r$ and center the origin. $P$ is the point $(0, r), Q$ is the upper point of intersection of the two circles, and $R$ is the point of intersection of the line PQ and the $x$ -axis. What happens to Ras $C_{2}$ shrinks, that is, as $r \rightarrow 0^{+} ?$