Three long wires parallel to the x axis carry currents as shown. If I = 30 A, what is the magnitude of the magnetic field at the origin? The top current (flowing to the right) is 4I and associated with y= 2m, the middle current (flowing to the left) is 3I and associated with y= –1m, and the bottom current (flowing to the right) is I and associated with y= –3m.