A short bar magnet placed in a horizontal plane has its axis aligned along north-south direction. Null points are found on the axis of the magnet at $20\,\text{cm}$ from the centre of magnet. The earth's magnetic field at the place is $B$ and angle of dip is $0^\circ$. If the total magnetic field on the normal bisector of the magnet $20\,\text{cm}$ from the centre of the magnet is $0.6\,\text{G}$, then the magnitude of $B$ is.