A magnetic needle of length 12 cm, suspended at its middle point by a thread, stays at an angle of 45^° with the horizontal. If the pole strength of…

A magnetic needle of length $\displaystyle 12$ cm , suspended at its middle point by a thread, stays at an angle of $\displaystyle 45^{\circ}$ with the horizontal. If the pole strength of the needle is $\displaystyle 2.4$ Am, what vertical force should be applied to an end so as to keep it in horizontal position? The horizontal component of the earth's magnetic field is $\displaystyle 20 \mu T$.