Chapter 21 - Heat Engines and Refrigerators - Exercises and Problems - Page 595: 30

$Q_H = 2500J$

We have $T_H =873K $ and $T_C =293K$ $\eta _{max} = 1- \frac{293}{873}$ $\eta = 0.66$ But given that $\eta = 60\% * \eta_{max}$ $\therefore \eta = 0.4 =40\%$ Also $\eta = W/Q_H$ $0.4 = 1000J/Q_H$ $Q_H = 2500J$