you have purchased an equipment costing $20,000. the equipment will be used for two years and at the end of two years its salvage value is expected to be $10,000 the equipment will be used 6,000 hours during the first and 8,000 hours during the second year. the expected annual net saving will be $30,000 during the first year and $40,000 during the second year. if your interest rate is 10% what would be the equivalent net savings per machine-hours?