d
${{\rm{i}}^2}{\rm{Rt}} = {\rm{mS}}\,\Delta \theta $ .........$(i)$
${(3{\text{i}})^2}{\text{Rt}} = {\text{mS}}\,\Delta {\theta ^1}$ .........$(ii)$
$\frac{( \text { ii ) } }{(\mathrm{i})} 9=\frac{\Delta \theta^{1}}{4} \Rightarrow \Delta \theta^{1}=4 \times 9=36^{\circ} \mathrm{\,C}$