In the fig. $\angle{PQR} = 100^{\circ}$ where $P, Q$ and $R$ are points on the circle with center $O$. Find $\angle{OPR}$

Question

$\begin{array}{1 1} (a)\; 10^{\circ} \\ (b)\; 20^{\circ} \\ (c)\; 25^{\circ} \\ (d)\; 30^{\circ} \end{array}$