What are the cost savings of purchasing and operating a $3.6…

What are the cost savings of purchasing and operating a $3.66 fluorescent lightbulb for its 9000 hour lifetime versus purchasing enough incandescent bulbs at $0.56 each – with each lasting 900 hours – and operating them for 9000 hours? Assume that electrity costs $0.13 per KWh and that the fluorescent bulb requires 11 W, whereas the incandescant bulb requires 60 W to operate.