Answer:
a)
, b) 
Explanation:
a) The coefficient of performance of a reversible refrigeration cycle is:

Temperatures must be written on absolute scales (Kelvin for SI units, Rankine for Imperial units)


b) The respective coefficient of performance is determined:



But:

The temperature at hot reservoir is found with some algebraic help:





Explanation:
Population inversion is a process of achieving more electrons in the higher energy state than the lower energy state. In order to achieve population inversion, we need to supply energy to the laser medium. The process of supplying energy to the laser medium is called pumping.
The precautions that should be taken to avoid the overloading of domestic electric circuits are:
- Do not put high voltage wires in one socket.
- Do not use many electric appliances of high power at the same time.
<h3>What are electric circuits?</h3>
Electric circuits are wires or devices that give electricity to devices that run on electricity. Running of electric devices should be done carefully because our body can come in contact with the current.
Thus, the precautions are to keep high voltage lines away from one socket. Use only a few high-power electric appliances at once.
To learn more about electric circuits, refer to the below link:
brainly.com/question/28221759
#SPJ4