Shamrock Industries changed from the double-declining-balance to the straight-line method in 2021 on all its equipment. There was no change in the assets salvage values or useful lives. Plant assets, acquired on January 2, 2018, had an original cost of $1,516,800, with a $105,600 salvage value and an 8-year estimated useful life. Income before depreciation expense was $292,800 in 2020 and $262,400 in 2021.