21. A gas tungsten arc-welding operation is performed on low-carbon steel. The unit melting energy for low-carbon steel can be determined by the methods of the previous chapter. Voltage = 20 V, current = 150 A, heat transfer factor = 0.55, and melting factor = 0.60. Filler metal wire of 4.0-mm diameter is added to the operation, so that the final weld bead consists of 60% filler and 40% base metal. If the travel speed in the operation is 5 mm/sec, determine (a) cross sectional area of the weld bead and (b) feed rate (mm/sec) at which the filler wire must be supplied.