explain step by step

Presented below are selected transactions at Gene Company for 2021. Jan. 1 Retired a piece of machinery that was purchased on January 1, 2011. The machine cost $75,000 on that date. It had a useful life of 10 years with no salvage value. June 30 Sold a computer that was purchased on January 1, 2018. The computer cost $30,000. It had a useful life of 5 years with no salvage value. The computer was sold for $10,500. July 31 Discarded a delivery truck that was purchased on January 1, 2017. The truck Cost $40,000. It was depreciated based on a 6-year useful life with a $4,000 Salvage value. Instructions Journalize all entries required on the above dates, including entries to update depreciation, where applicable, on assets disposed of. Gene Company uses straight-line depreciation. (Assume depreciation is up to date as of December 31, 2020.)