Following figures show the arrangement of bar magnets in different configurations. Each magnet has magnetic…

$\left(a\right)$ $M_{\mathrm{n}\mathrm{e}\mathrm{t}}=\sqrt{m^2+m^2+2\mathrm{m}\mathrm{m}\cos {90}^{\mathrm{o}}}=\sqrt{2} \mathrm{m}$

$\left(b\right)$ $M_{\mathrm{n}\mathrm{e}\mathrm{t}}=m-m=0$

$\left(c\right)$ $M_{\mathrm{n}\mathrm{e}\mathrm{t}}=\sqrt{m^2+m^2+2 \mathrm{m}\mathrm{m}\cos {30}^{\mathrm{o}}}=m\sqrt{2+\sqrt{3}}$
$\left(d\right)$ $M_{\mathrm{n}\mathrm{e}\mathrm{t}}=\sqrt{m^2+m^2+2 \mathrm{m}\mathrm{m}\cos {60}^{\mathrm{o}}}=\sqrt{3} \mathrm{m}$
is configuration $\left(C\right) \theta$ in least so $M_{\mathrm{n}\mathrm{e}\mathrm{t}}$ is maximum.