Relative to an origin \(O\), the position vector of point \(P\) is \(3\mathbf{i}-2\mathbf{j}\) and the position vector of point \(Q\) is \(8\mathbf{i}+13\mathbf{j}\).

(a) The point \(R\) is such that \(\overrightarrow{PQ}=5\overrightarrow{PR}\). Find the unit vector in the direction \(\overrightarrow{OR}\).

(b) The position vector of \(S\) relative to \(O\) is \(\lambda\mathbf{j}\). Given that \(RS\) is parallel to \(PQ\), find the value of \(\lambda\).