Two methods can be used to produce expansion anchors. method a costs $80,000 initially and will have a $15,000 salvage value after 3 years. the operating cost with this method will be $30,000 in year 1, increasing by $4000 each year. method b will have a first cost of $120,000, an operating cost of $8000 in year 1, increasing by $6500 each year, and a $40,000 salvage value after its 3-year life. at an interest rate of 12% per year, which method should be used on the basis of a present worth analysis?