On January 1, 2022 Romano Company purchased a machine for $180,000. It is estimated that the machine will have a useful life of 4 years with a salvage value of $10,000 at the end of its useful life. It is also estimated that the machine will produce 125,000 units over its useful life. Actual usage was as follows: 2022, 45,000 units; 2023, 35,000 units; 2024, 25,000 units; and 2025, 20,000 units. Required: Calculate the annual depreciation expense under each of the following methods using an excel spread sheet: Straight-line Declining-balance Sum of the years' digits Units-of-activity