Practice 8.6 Sam Co. purchased a new machine for $40,000 on 10/1/X1. The machine has an estimated useful life of 5 years or 50,000 machine hours. Its estimated salvage value is $5,000. Sam uses the machine 5,000 hours in 20X1, 15,000 in 20X2, 20,000 in 20X3, 5,000 in 20X4. Calculate depreciation expense each year for the first 4 years using the straight-line, units of activity (production) and the double declining balance methods