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4.2 A warm air gas fired furnace is to be selected for installation in a single family dwelling. Two furnaces are proposed for the installation. A natural draft burner type would cost $1500 to install. The estimated annual fuel cost would be $500. The alternative would be to install a pulse combustion furnace that would use 20% less fuel. It would cost $3000 to install. Annual maintenance fees would be 1% of the first cost. The estimated salvage value after 20 years is 10% of the first cost. Using the present worth method, compare the two alternatives using an annual interest rate of 12%