On January 1, 2020 Lucky Inc. purchased equipment at a cost of $120,000. The estimated useful life in years is 4 years and the estimated useful life in units is 50,000 units. At the time of the purchase, the estimated salvage value was $20,000. Instructions: Calculate depreciation expense for 2020 and 2021 using the straight-line method, the doubledeclining method and the units-of-activity method. Assume that the activity was as follows; In year 2020,12,000 units were produced and in year 2021,15,000 units were produced