Please help me with the below!!!!!!!!

Various cable types and sizes have been used in the electrical installation in commercial building. Discuss the following:
a) The advantages and disadvantages of various cable types.
b) Stages and procedures for sizing these cables, taking into considerations the method of installation, ambient temperature, the anticipation for future demand, grouping factor and any other considerations that you might want to include to elaborate your answer.

 

What you are looking for are wiring codes. The best reference is the NEC. Wikipedia may get you a start - http://en.wikipedia.org/wiki/Electrical_wiring

 

look in the BS7671 its all in there