What is the expression for the axial field of a bar magnet for very l…

-\(\frac{μ_{o}}{4π} \frac{M}{r^{3}}\)

\(\frac{μ_{o}}{4π} \frac{M}{r^{3}}\)

-\(\frac{μ_{o}}{4π} \frac{2M}{r^{3}}\)

\(\frac{μ_{o}}{4π} \frac{2M}{r^{3}}\)