Could you please explain the calculations in detail for Book Value Beginning of Year (2019, 2020, 2021) and Accumulated Depreciation (36,000 and 57,600 and 70,560)? I do not understand how these numbers came from.

3-2. Marlow Company purchased equipment on January 1, 2019 for $90,000. It is estimated that the equipment will have a $5,000 residual value at the end of its 5-year useful life. It is also estimated that the equipment will produce 100,000 units over its 5-year life. Instructions Answer the following independent questions. 1. Compute the amount of depreciation expense for the year ended December 31, 2019, using the straight-line method of depreciation. 2. If 16,000 units of product are produced in 2019 and 24,000 units are produced in 2020, what is the book value of the equipment at December 31, 2020? The company uses the units-of- activity depreciation method. 3. If the company uses the double-declining-balance method of depreciation, what is the balance of the Accumulated Depreciation Equipment account at December 31, 2021? 3-2 1. .000 per year C-s Straight-line method: = Years C-s Units-of-activity method: = Units ($90,000 - $5,000) 5 year) ($90,000 - $5,000) 100,000 units 2. = $0.85 per unit = 2019 16,000 units x $.85 2020 24,000 units x $.85 Accumulated depreciation $13,600 = 20,400 = $34.000 Cost of asset Less: Accumulated Depreciation Book value $90,000 34.000 $56.000 (90,000 -34,000) 3. Double-declining-balance method: Book Value Beginning Declining of Year Balance Rate 2019 $90,000 40% 2020 54,000 40% 2021 32,400 40% Depreciation Expense $36,000 21,600 12,960 Accumulated Depreciation $36,000 57,600 70,560