Circle and triangle

Above shows a triangle $XYZ$ with $XY= 18, YZ=16, XZ=14$ . The bisector of angle $X$ meets the straight line $YZ$ at point $W$ .

The circle passing through point $X$ and touching $YZ$ at $W$ cuts $XY$ and $XZ$ at points $M$ and $N$ respectively.

Find the distance $MN$ .