Explanation

(c) If dipole be rotated from an initial orientation $\theta = \theta_{1}$ to final orientation $\theta = \theta_{2}$, the total work required is
$W = \int_{\theta_{1}}^{\theta_{2}}{pE\sin{\theta\ d\theta}}$
$W = pE\left\lbrack - \cos\theta \right\rbrack_{\theta_{1}}^{\theta_{2}}$
Where $p$ is dipole moment and $E$ the electric field.
In first case.
$W = pE\left( 1 - \cos{60{^\circ}} \right)$
$W = pE\left( 1 - \frac{1}{2} \right) = \frac{pE}{2}$
$\Longrightarrow pE = 2W$
In second case,
$W_{2} = pE\left( 1 - \cos{180{^\circ}} \right)$
$W_{2} = 2W(1 + 1) = 4W$