Three blocks A, B and C are lying on a smooth horizontal surface, as shown in the figure. A and B have equal masses, m while C has mass M, Block A is given an initial speed $\upsilon $ towards B due to which it collides with B perfectly inelastically. The combined mass collides with C, also perfectly inelastically ${5 \over 6}$th of the initial kinetic energy is lost in whole process. What is value of M/m ?