A 30-kg block of ice at 0° C is sliding on a horizontal surface. The initial speed of the ice is 6.1 m/s and the final speed is 4.5 m/s. Assume that the part of the block that melts has a very small mass and that all the heat generated by kinetic friction goes into the block of ice. Determine the mass of ice that melts into water at 0° C.