In $\Delta PQR$,M and N are points on sides PQ and PR respectively such that PM=15 cm and NR=8 cm.If PQ=25 cm and PR=20 cm,then MR is ________ QR

Question

$\begin{array}{1 1}\text{perpendicular to}\\\text{parallel to}\\\large\frac{1}{2}\normalsize\text{ of}\\\text{None of these}\end{array} $