a portable concrete test instrument used in construction for evaluating and profiling concrete surfaces (macrs-gds 5-year property class) is under consideration by a construction firm for $26,000. the instrument will be used for 6 years and be worth $2,750 at that time. the annual cost of use and maintenance will be $8,000. alternatively, a more automated instrument (same property class) available from the manufacturer costs $31,500, with use and maintenance costs of only $7,000 and salvage value after 6 years of $4,000. the marginal tax rate is 25%, and marr is an after-tax 12%.