A sphere of mass M and radius R is held on the inner wall of a hollow sphere of mass 4M and radius 6R .The bigger sphere is kept on a smooth horizontal table and the centres of the two spheres lie on horizontal line.The system of two spheres is released from this position. The smaller sphere slides on the inner smooth wall to reach the other extreme position (shown in dotted line).The displacement of the centre of the larger sphere as the smaller sphere moves from one extreme to another is xcm. Value of x is: ( Take R=4.5cm) qquad y qquad yR Delta M