Two 8 mm thick steel places are placed 5 mm apart and welded by a butt joint. Welding is carried out at 0 V and speed of 5 mm/sec. heat transfer efficiency is 0.80. if the heat required to melt steel is 10 J/mm3 and melting efficiency is 0.625. the weld current (in Amperes) will be
(a) 100 (b) 200
(c) 300 (d) 400