On January 1, 2016, Weiner Company bought a machine for $60,000. It was then estimated that the useful life of the machine would be eight years with a salvage value of $8,000. On January 1, 2020, it was decided that the machine's total life from acquisition date should have been only six years with a salvage value of only $2,000. The company used straight-line depreciation.

a.	If an adjusting entry is necessary on January 1, 2020, prepare it.
b.	Compute depreciation expense for 2020.