Phoenix Company acquired machinery costing $36,000 on January 2, 2019. At that time Phoenix estimated that the useful life of the equipment was 8 years and that the residual value would be $6,000 at the end of its useful life. Compute depreciation expense for this asset for 2019, 2020, and 2021 using the

a. Straight-line method.

b. Double-declining-balance method.

c. Assume that on January 2, 2021, Phoenix revised its estimate of the useful life to 12 years and changed its estimate of the residual value to $1,000. What effect would this have on depreciation expense in 2021 for each of the above depreciation methods?