Interaction energy and two adjecent dipoles

$\mathrm{u}_{1}=\frac{\mathrm{kp}^{2}}{\mathrm{a}^{3}} \uparrow \uparrow, \mathrm{u}_{2}=-\frac{\mathrm{kp}^{2}}{\mathrm{a}^{3}} \uparrow \downarrow$

interaction energy of the two end dipoles

$\mathrm{u}_{3}=\frac{\mathrm{kp}^{2}}{8 \mathrm{a}^{3}} \uparrow \uparrow ; \quad \mathrm{u}_{4}=-\frac{\mathrm{kp}^{2}}{8 \mathrm{a}^{3}} \uparrow \downarrow$

Total interaction energy in $\mathrm{I}$ configuration

$U_{1}=U=2 u_{1}+u_{3}=\frac{17 k p^{2}}{8 a^{3}}$          .........$(i)$

Total interaction energy in $\mathrm{II}$ configuration

$\mathrm{U}_{2}=\mathrm{u}_{1}+\mathrm{u}_{2}+\mathrm{u}_{4}=\frac{-\mathrm{kp}^{2}}{8 \mathrm{a}^{3}}$         ........$(ii)$

Work done electric forces

$=U_{1}-U_{2}=\frac{18}{8} \frac{\mathrm{kp}^{2}}{\mathrm{a}^{3}}=\frac{18}{17} \mathrm{U}$