Answer:
For 1 week total cost will be equal to 0.2912
Step-by-step explanation:
We have given power P = 40 watt
Light is on from 6 pm to 7 am
So total time = 13 hours
We know that energy is given by

So energy will be

We have given cost per KWh is 0.08
So total cost per day will be = 0.08 ×0.520 = 0.0416
For 1 week that is for 7 day total cost will be = 7×0.0416 = 0.2912