hi my name is christina and i have an electrical question i need help with.

i am taking power engineering electrical 188.
the question is:
how much will ity cost to use 6 lamps of 100 W each if they burn for 5 hours each evening in a month (30 days). the cost of electricity is 0.04 cents per kwh?
how do u solve this question? the answer is $3.60

(6 lamps) * (100W/lamp) * (5 hours/day) * (30 days)

You will end up with a number of watt hours. Convert watt hours to kilo watt hours. Multiply that number by $0.04