Is the coefficient of performance of a refrigerator constant?

In a refrigerator,one removes heat from a lower temperature and deposits it to the surroundings at a higher temperature. In this process,mechanical work has to be done,which is provided by an electric motor. If the motor is of $1\,kW$ power and heat is transferred from $-3\,^{\circ}C$ to $27\,^{\circ}C$,find the heat taken out of the refrigerator per second,assuming its efficiency is $50\%$ of a perfect engine.

The power of a refrigerator that can make $15 \ kg$ of ice at $0^{\circ}C$ from water at $30^{\circ}C$ in one hour is: (in $W$)

What is the coefficient of performance of a refrigerator operating between $30^{\circ}C$ and $0^{\circ}C$?

The equation $\beta = \frac{Q_2}{Q_1 - Q_2}$ is true or false?

$A$ Carnot engine,having an efficiency of $\eta = 1/10$ as a heat engine,is used as a refrigerator. If the work done on the system is $10 \ J$,the amount of energy absorbed from the reservoir at a lower temperature is ....... $J$.