A short bar magnet has a length 2l and a magnetic moment 10 Am². Find the magnetic field at a distance of z = 0.1 m from its centre on the axial line. Here, l is negligible as compared to z.

A) 8π 10^(-3) T
B) 4π 10^(-3) T
C) 2π 10^(-3) T
D) π 10^(-3) T