The resistance spot welding of two thick metal sheets is performed using the welding current of 9950 A. The contact resistance at the interface of the metal sheets is 0.00015 Ω. The volume of weld nugget formed after welding is 72 mm3. Considering the heat required to melt unit volume of metal is 8 J/mm3, Assuming that the heat lost to the surrounding base metal is 454 J. If all other losses  are negligible then  the thermal efficiency of the welding process is_______ % (round off to one decimal place).