$\eta=1-\frac{{T}_{2}}{{T}_{1}}$
$\frac{1}{4}=1-\frac{{T}_{2}}{{T}_{1}}$
$\frac{{T}_{2}}{{T}_{1}}=\frac{3}{4} \ldots$ $(i)$
$\frac{1}{2}=1-\frac{{T}_{2}-58}{{T}_{1}}$
$\frac{{T}_{2}}{{T}_{1}}-\frac{58}{{T}_{1}}=\frac{1}{2}$
$\frac{3}{4}=\frac{58}{{T}_{1}}+\frac{1}{2}$
$\frac{1}{4}=\frac{58}{{T}_{1}} \Rightarrow {T}_{1}=232$
${T}_{2}=\frac{3}{4} \times 232$
${T}_{2}=174\, {K}$

