We have seen that the heart produces a magnetic field that can be used to diagnose problems with the heart. The magnetic field of the heart is a dipole field produced by a loop current in the outer layers of the heart. Suppose that the field at the center of the heart is \(90 \mathrm{pT}\) (a pT is \(10^{-12} \mathrm{~T}\) ) and that the heart has a diameter of approximately \(12 \mathrm{~cm}\). What current circulates around the heart to produce this field?