(c) As $\eta = 1 - \frac{T_{2}}{T_{1}}\ \ \therefore\ \frac{T_{2}}{T_{1}} = 1 - \eta = 1 - \frac{10}{100} = \frac{90}{100}$ or $T_{1} = \frac{100T_{2}}{90}$ $= \frac{100}{90} \times 270 = 300\ K$
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