You are comparing LED and CFL bulbs. A 100 watt CFL bulb costs $1.00 and lasts 1,500 hours, while a comparable LED bulb of 15 watts costs $3.00 and lasts 4,000 hours. There are 1,000 watt in a kilowatt and a unit of electricity (1,000 watts-hour) costs 12 cents. If you use each bulb for 500 hours in a year and require a return of 15% what are the equivalent annual cost of each bulb?