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 B=B0t2 where B0=4T/sec2 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 x×10−1 Find the value of x.