Question 21In the adjoining figure, the triangle $ABC$ is a right triangle with $\angle BCA=90^\circ.$ Median $CM$ is perpendicular to median $BN,$ and side $BC=s.$ The length of $BN$ is $s\sqrt2$$\frac32s\sqrt2$$2s\sqrt2$$\frac{s\sqrt5}{2}$$\frac{s\sqrt6}{2}$
