Reversed Carnot Cycle
The Reversed Carnot Cycle is a theoretical thermodynamic cycle that consists of four processes: two isothermal processes and two adiabatic processes. It is used to analyze the performance of heat engines and refrigerators.

Coefficient of Performance (COP)
The coefficient of performance (COP) is a measure of the efficiency of a heat pump or refrigerator. It is defined as the ratio of the desired output, such as the heat extracted or the cooling effect, to the required input, such as the work done or the energy consumed.

COP of a Refrigerator
For a refrigerator working on the Reversed Carnot Cycle, the COP is given by the equation:
COP = 1 / (T_H / T_L - 1)
where T_H is the temperature of the high-temperature reservoir and T_L is the temperature of the low-temperature reservoir.

Given that the COP of the refrigerator is 3, we can substitute this value into the equation to find the temperatures ratio:
3 = 1 / (T_H / T_L - 1)
T_H / T_L - 1 = 1/3

COP of a Heat Pump
When the refrigerator works as a heat pump, the COP is defined as the ratio of the heat extracted from the low-temperature reservoir to the work done on the system:
COP_heat_pump = Q_L / W

To find the COP of the refrigerator when it works as a heat pump, we need to determine the values of Q_L and W. Since the COP of the refrigerator is 3, we know that Q_L = 3W.

Calculating COP of the Heat Pump
Now we can substitute the value of Q_L into the COP equation:
COP_heat_pump = Q_L / W
COP_heat_pump = 3W / W
COP_heat_pump = 3

Therefore, the COP of the refrigerator when it works as a heat pump is 3.

Conclusion
The correct answer is option 'A' (4) is incorrect because the COP of the heat pump is not 4 but 3. The COP remains the same for both the refrigerator and the heat pump since it is determined by the temperatures ratio and not by the specific mode of operation.