Three long, straight electrical cables, running north and south, are tightly enclosed in an insulating sheath. One of the cables carries a 21.3 A current southward; the other two carry currents of 17.2 A and 10.8 A northward.
Use Ampere’s law to calculate the magnitude of the magnetic field at a distance of 10.0 \rm m from the cables.
Express your answer to two significant figures and include the appropriate units.