solution

The Biltmore Garage has lights in places that are difficult to reach. Management estimates that it costs about $2 to change a bulb. Standard 100-watt bulbs with an expected life of 1000 hours are now used. Standard bulbs cos $1. A long-life bulb that requires 90 watts for the same effective level of light is available. Long-life bulbs cost $3. The bulbs that are difficult to reach are in use for about 500 hours a month. Electricity costs $0.07/kilowatt-hour payable at the end of each month. Biltmore uses a 12 percent MARR (1 percent per month) for projects involving supplies.