The coefficient of performance (COP) or $\beta$ of a refrigerator working between temperatures $T_1$ (higher) and $T_2$ (lower) is given by: $\beta = \frac{T_2}{T_1 - T_2}$ Given: $T_2 = 4^{\circ}\text{C} = 277 \text{ K}$ $T_1 = 30^{\circ}\text{C} = 303 \text{ K}$ $\beta = \frac{277}{303 - 277} = \frac{277}{26} \approx 10.65$ Also, $\beta$ is defined as the ratio of heat extracted ($Q_2$) to the work done ($W$): $\beta = \frac{Q_2}{W}$ Given rate of heat extraction $\dot{Q}_2 = 600 \text{ cal/s}$. Convert to Joules: $\dot{Q}_2 = 600 \times 4.2 \text{ J/s} = 2520 \text{ W}$. The power required ($P$) corresponds to the work done per second ($\dot{W}$): $P = \frac{\dot{Q}_2}{\beta} = \frac{2520}{10.65}$ $P \approx 236.5 \text{ W}$