Answer:
Depreciation expense: 
 Year 1 = $27,500 
 Year 2 = $27,500 
 Year 3 = $37,500 
 Year 4 = $37,500 
Step-by-step explanation:
 Annual depreciation is computed using the equation given below: 
 Annual depreciation = {Cost of machine - Salvage value} ÷ Estimated life 
 = {$135,000 - $25,000} ÷ 4 
= $27,500 
Depreciation of year 1 is $27,500 
Cost of machine in year 2 is {$135,000 - $27,500} = $107,500 
Depreciation of year 2 is $27,500 
Cost of machine in year 3 is {$107,500 - $27,500} = $80,000
 Annual depreciation is computed using the equation given below: 
 Annual depreciation = {Cost of machine - Salvage value} ÷ Remaining estimated life 
 = {$80,000 - $5,000} ÷ 2 
 = $37,500 
 Depreciation expense of year 3 is $37,500 
 Cost of machine in year 4 is ($80,000 - $37,500) = $42,500 
Depreciation expense of year 4 is $37,500 
Cost of machine at the end of year 4 is ($42,500 - $37,500) = $5,000