Prepare general journal entries to record the following events: (Show your calculations)

Oct 1, 2019	Purchased a machine for $90,000 cash. The machine had a salvage value of $10,000 and an estimated life of 10 years.
Dec 31, 2019	Recorded depreciation expense for the year.
Jan 1, 2020	Added a computer control device to the machine for a cost of $5,400. The control improved the quality of the machine's operation, extended its service life for 2 years beyond the original estimate, and will provide a revised salvage value of $6,000 at the end of the machines life.
Jul 1, 2020	The machine was cleaned, inspected and two worn parts were replaced at a cost of $1,500. No estimates of life or salvage value changed because of this routine maintenance.
Dec 31, 2020	Depreciation expense was recorded for the year.