SMO 2005 Senior Round 1 Question 6

In the diagram, $P,Q,R$ are three points on the circle whose centre is $O$. The lines $PO$ and $QR$ are produced to meet at $S$. Suppose that $RS=OP$, and $\angle PSQ=12^\circ$ and $\angle POQ=x^\circ$. Find the value of $x$.