d
Here, $\eta_{1}=1-\frac{\mathrm{T}_{2}}{\mathrm{T}_{1}}$
$0.25=1-\frac{\mathrm{T}_{2}}{\mathrm{T}_{1}} \Rightarrow \frac{1}{4}=1-\frac{\mathrm{T}_{2}}{\mathrm{T}_{1}}$
$\frac{\mathrm{T}_{2}}{\mathrm{T}_{1}}=1-\frac{1}{4}=\frac{3}{4}$ $ . .(\mathrm{i})$
According to question.
$\eta_{2}=2 \eta_{1},$ and $\mathrm{T}_{2}=\mathrm{T}_{2}-58^{\circ} \mathrm{C}$
$\therefore \quad 2 \times \frac{1}{4}=1-\frac{\left(\mathrm{T}_{2}-58^{\circ} \mathrm{C}\right)}{\mathrm{T}_{1}}$
$\Rightarrow 1-\frac{1}{2}=\frac{\mathrm{T}_{2}-58^{\circ} \mathrm{C}}{\mathrm{T}_{1}}$
$\frac{1}{2}=\frac{T_{2}}{T_{1}}-\frac{58^{\circ}}{T_{1}} \Rightarrow \frac{3}{4}-\frac{1}{2}=\frac{58}{T_{1}}$
$\Rightarrow \mathrm{T}_{1}=232^{\circ} \mathrm{C}$