\item $I = (\textrm{charge}) \cdot (\textrm{loops per time})
\stackrel{1/T=\omega_L/2\pi}{=}
(Ze)(\frac{1}{2\pi}\frac{-e}{2m}B)$\\
- $\mu=IA=I2\pi<\rho^2>=-\frac{Ze^2B}{4m}<\rho^2>$\\
+ $\mu=IA=I\pi<\rho^2>=-\frac{Ze^2B}{4m}<\rho^2>$\\
$<x^2>=<y^2>=<z^2> \Rightarrow <r^2>=3<x^2>=3<y^2>$\\
$<\rho^2>=<x^2>+<y^2>=\frac{2}{3}<r^2>$\\
$\mu=-\frac{Ze^2B}{6m}$