26. Five mark exercise problem VIII

\(PQRS\) is a rhombus. Its diagonals \(PR\) and \(RS\) intersect at the point \(M\) and satisfy \(QS = 2PR\). If the coordinates of \(S\) and \(M\) are \((1, 1)\) and \((2, -1)\), respectively, find the coordinates of \(P\).