(c) As $\eta = 1 = \frac{T_{2}}{T_{1}}\ $ $\therefore\ \frac{50}{100} = 1 = \frac{500}{T_{1}}\ or\ T_{1} = 1000K$ Again, $\frac{60}{100}\ = 1 - \frac{T_{2}}{1000}$ Or $T_{2} = 400\ K$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.