In a certain city, electricity costs $0.15 per kw·h. what is the annual cost for electricity to power a lamp-post for 6.00 hours per day with (a) a 100.-watt incandescent light bulb (b) an energy efficient 25-watt fluorescent bulb that produces the same amount of light? assume 1 year = 365 days.

(a) Power of bulb is 100 W, converting this into kW.

Thus,

The bulb is used for 6 hours per day for a year, in 1 year there are 365 days thus, total hours will be:

Electricity used will depend on power and number of hours as follows:

The cost of electricity is $0.15 per kW.h thus, cost of electricity for 219 kW.h will be:

Therefore, annual cost of incandescent light bulb is

(b) Power of bulb is 25 W, converting this into kW.

Thus,

The bulb is used for 6 hours per day for a year, in 1 year there are 365 days thus, total hours will be:

Electricity used will depend on power and number of hours as follows:

The cost of electricity is $0.15 per kW.h thus, cost of electricity for 54.75 kW.h will be:

Therefore, annual cost of fluorescent bulb is .

i'm pretty sure its b i might be wrong though!