Halliday, Resnick & Walker — Magnetic Fields: Problem 28

28 Figure 28-33 shows a current loop $ABCDEFA$ carrying a current $i = 3.00\text{ A}$. The sides of the loop are parallel to the coordinate axes shown, with $AB = 20.0\text{ cm}$, $BC = 30.0\text{ cm}$, and $FA = 10.0\text{ cm}$. In unit-vector notation, what is the magnetic dipole moment of this loop? (Hint: Imagine equal and opposite currents $i$ in the line segment $AD$; then treat the two rectangular loops $ABCDA$ and $ADEFA$.)