3.2 kg block is given an initial velocity of 12 m/s across horizontal surface. after travels 8 m speed is 2.4 m/s. determine coefficient of friction bewern block and surface and how far it travels before coming to rest

lost KE=workbyfricton

1/2 m 12^2-1/2 m 2.4^2=mu*m*g*8

notice m divide out, solve for mu