Answer:
Depreciation for 2018 is = $15,120.60
Depreciation for 2019 is  = $13,133.84 
Depreciation for 2020 is = $10,401.04
Depreciation for 2021 is = $10,660.65
Explanation:
solution
we know here 
Depreciation under Units of production method is    
Depreciation is = (Cost - Salvage value) × (No of units produced ÷ Expected units of production)
put here value for each year 
Depreciation for 2018 is = (42700-1708) × (553300 ÷ 1500000) 
Depreciation for 2018 is = $ 15,120.60
  
Depreciation for 2019 is = (42700-1708) ×  (480600 ÷ 1500000) 
Depreciation for 2019 is  = $ 13,133.84  
  
Depreciation for 2020 is = (42700-1708)×  (380600 ÷ 1500000) 
Depreciation for 2020 is = $ 10,401.04	
  
Depreciation for 2021 is = (42700-1708)×  (390100 ÷ 1500000) 
Depreciation for 2021 is = $ 10,660.65