Answer
$U_{1}>U_{2}>U_{3}$
Work Step by Step
$U_{1}>U_{2}>U_{3}$
$U_{1}$ will be positive and greatest since all forces among dipoles are repulsive. $U_{2}$ is negative as potential energy of first and second dipole pair cancels out potential energy of interaction of first and third, that is negative. In (c) effect of attraction is greatest.
