A square hole is to be cut using ECM through a plate of low alloy steel that is 12 mm thick. The hole is 35 mm on each side, but the electrode used to cut the hole is slightly less than 35 mm on its sides to allow for overcut, and its shape includes a hole in its center to permit the flow of electrolyte and to reduce the area of the cut. This will produce a center core that can be removed after the tool breaks through. This tool design results in a frontal area of 245 mm2 . The applied current = 1200 amps.

Using an efficiency of 95%, how long will it take to cut the hole?