Aball of putty of mass m travels at speed v = 0.8 towards another ball of putty of mass 2m, which is at rest. after the collision the balls are stuck together and the combined lump has mass m' and speed v'. (a) by comparing the components of the total 4-momenta before and after the collision find the speed, v', of the combined lump after the collision. (b) by comparing the magnitudes of the total 4-momenta before and after the collision find the mass, m' of the combined lump after the collision. (c) quantitatively compare these results with those expected from a non-relativistic calculation. (d) is energy conserved in the non-relativistic calculation? is energy conserved in the relativistic calculation? explain your reasoning.