A non conducting ring of mass m = 1 kg and radius R = 10 cm has a charge Q = 2 C uniformly distributed over its circumference. The ring is placed on rough horizontal surface such that plane of the ring is parallel to the surface. A vertical magnetic field $\mathrm{B}={\mathrm{B}}_0{\mathrm{t}}^2$ where ${\mathrm{B}}_0=4\mathrm{T}/{\sec }^2$ is switched on. After 5 sec, after switching on the magnetic field the ring is just about to rotate about vertical axis through the centre. The coefficient of friction  between the ring and the surface is  found to be $\mathrm{x}\times {10}^{-1}$ Find the value of x.