How much does it cost (in dollars) to operate one street lamp in Tempe, Arizona for one year?

Street lamps shine brighter than a household 100 W bulb.

1. Estimate the wattage of one street lamp. (answer is 250)

2. Estimate the number of hours, a street lamp is lit for 1 year.

3. Estimate the cost of electricity (in dollars) per kW-hour in Tempe.

4. Estimated cost (in dollars) to operate a street lamp in Tempe for one year.

Please state how you got each answer!