At times in history, people expressed concerns about the magnetic fields created by the currents running through household wires. How strong are such fields? Recall that a cable running through your wall consists of a "hot" wire, a "neutral" wire, and a ground wire. Typically current doesn't flow through the ground wire. Current travels down the hot wire and back in the neutral wire, and both wires have the same current. Assume that the hot and neutral wires are separated by 4mm, and that the current is DC (it's really AC, but the magnetic fields won't differ much at an instant in time). Most household wires are designed to have a maximum current of 15A.
Sketch a diagram that shows the B from the hot wire, the B from the neutral wire, and the net magnetic field at point P. You'll need to assign a coordinate system to orient the direction of your vectors with respect to the direction of the wires.