$($a$)$

$($b$)$

$($c$)$

$($d$)$

The potential energy of two interacting magnetic moments, $m_1$ and $m_2,$ that are not at the same position is given by

$U=-\frac{{}_0}{4r^5}[3(m_1*r)(m_2*r)-(m_1*m_2)r^2]$

Figure shows four different configurations of identical dipole moments that are the same distance away from one another. Arrange the four configurations of two dipole moments, in order of increasing energy.