(A) (SI units) A resistance spot welding operation makes a series of spot welds between two sheets of aluminum, each 3.0 mm thick. The unit melting energy for aluminum- 2.90

J/mm'. Welding current-6000 amps, resistance = 75 micro-ohms, and time duration = 0.15 sec. Each weld nugget = 5.0 mm in diameter with an average thickness - 3.5 mm. How much of the total energy generated is used to form the weld nugget?