The Attempt at a Solution
2.4 Total efficiency = (45/100x86/100)x100% = 38.7%
2.7 3.1kWx4hoursxR4.75/kWh = R58.90
I don't feel satisfied that these answers are correct, probably because they are not.
The answer to 2.6 concerns me most.
When can I use the equations P=I^2R and E=I^Rt?