Three infinite vertical wires are arranged in a straight line viewed from the top. Wire 1 (Left) carries 2A, Wire 2 (Middle) carries 4A, and Wire 3 (Right) carries 2A. All currents flow out of the page. The distance between adjacent wires (1-2 and 2-3) is 10cm. Find the magnitude of the net magnetic force per unit length on the Middle wire.