A TIG (gas tungsten arc) welding operation runs at 300 A and 20 V. The melting factor is 0.5, the heat-transfer factor for TIG is 0.7 and the unit melting energy of the metal is 10 J/mm³. Determine (a) the arc power in W, (b) the rate of heat used for welding in W and (c) the volume rate of metal welded in mm³/s.