A square hole is to be cut using ECM through a plate of pure copper (valence = 1) that is 20 mm thick. The hole is 25 mm on each side, but the electrode used to cut the hole is slightly less that 25 mm on its sides to allow for overcut, and its shape includes a hole in its center to permit the flow of electrolyte and reduce the area of the cut. This tool design results in a frontal area of 200 mm2. The applied current = 1000 amps. Using an efficiency of 95%, determine how long it will take to cut the hole.