# A bar magnet of 10 cm long is kept with its north (N)-pole pointing North. A neutral point is formed at a distance of 15 cm from each pole. Given the horizontal component of earth's field is $0.4$ Gauss, the pole strength of the magnet is :

$\begin {array} {1 1} (1)\;9\;amp-m & \quad (2)\;6.75\;amp-m \\ (3)\;27\; amp-m & \quad (4)\;13.5\;amp-m \end {array}$

$(4)\;13.5\;amp-m$