Below are two cases related to the depreciation of plant and equipment. In both cases the company has a December 31 year-end.
Case A: A machine was acquired on January 1, 2017, for $4,000,000. At that time it was estimated the machine would last eight years and have a residual value of $500,000. The company uses the straight-line method to record depreciation. Due to reduced levels of activity during 2019, management revised the estimate of useful life to 10 more years (the machine was to be operational until December 31, 2028, 12 years in total) and its residual value would be $300,000.
Case B: Same as Case A, except the company uses the declining-balance method. The rate used will be 2 / 8 years, or 25%, for the first two years and then 2 / 12 years, or 16.67%, thereafter.

Required:
For each case, prepare the journal entries for depreciation for 2017 and 2019.