The points \(A\) and \(B\) have position vectors \(\mathbf{a}\) and \(\mathbf{b}\) respectively, relative to an origin \(O\). The point \(P\) divides the line segment \(OA\) in the ratio \(1:3\), and the point \(R\) divides the line segment \(AB\) in the ratio \(1:2\). Given that \(PRBQ\) is a parallelogram, determine the position vector of \(Q\).