Please explain the calculations for all the numbers in (Dec 31).

3-4. Presented below are selected transactions for Corbin Company for 2020. Jan. 1 Received $3,000 scrap value on retirement of machinery that was purchased on January 1, 2009. The machine cost $90,000 on that date, and had a useful life of 10 years with no residual value. April 30 Sold a machine for $31,000 that was purchased on January 1, 2017. The machine cost $90,000, and had a useful life of 5 years with no residual value. Dec. 31 Discarded a business automobile that was purchased on April 1, 2016. The car cost $42,000 and was depreciated on a 5-year useful life with a residual value of $2,000. Instructions Journalize all entries required as a result of the above transactions. Corbin Company uses the straight-line method of depreciation and has recorded depreciation through December 31, 2019. 3-4 Jan. 1 Cash... Accumulated Depreciation Equipment... Equipment... Gain on Disposal of Plant Assets... 3,000 90,000 90,000 3,000 April 30 6,000 6,000 years Jan 2020 - April 20 20 Depreciation Expense.... Accumulated Depreciation Equipment..... ($90,000 ~ 1/5 ~ 4/12 = $6,000) Jan-April 90,000 - 5 years Cash.... 31,000 Accumulated Depreciation-Equipment ($18,000 x 3 1/3). 60,000 19 2019 2020 Equipment.. Gain on Disposal of Plant Assets ($31,000 - $30,000).. 90000 - 60,000 = 30,000 Depreciation Expense..... 8,000 Accumulated Depreciation Equipment.. 90,000 1,000 Dec. 31 8,000 Accumulated Depreciation Equipment ($8,000 4 3/4).... Loss on Disposal.. Equipment...... 38,000 4,000 42,000