Two very long, straight, parallel wires carry currents that are directed perpendicular to the page, as in the figure below. Wire 1 carries a current I1 into the page (in the -z direction) and passes through the x axis at x=+a. Wire 2 passes through the x axis at x=-2a and carries an unknown current I2. The total magnetic field at the origin due to the current-carrying wires has the magnitude (2*permeability of free space)/(2*pi*a) The current I2 can have either of two possible values. I know how to get the magnetic field at a point P for one current carrying wire, but I don't understand how to get the magnetic field at a point P for two current carrying wires. I know that the magnetic field at a point P for one current carrying wire is B=(permeability of free space * I)/(2*pi*a). I need some help...Any help would be great. Thx in advance!