Show frmulas do not use excel

Question 4: Henry has an assignment from his boss at Czech Glass and Wood Sculpting to evaluate depreciation methods for writing off the $300.000 first cost of a newly acquired Trotec CO2 laser system for engraving and cutting. No salvage is estimated at end of lifetime. Compare the PW of depreciation for DDB-to-SL switching (for a lifetime of n=8 years) with the PW for MACRS depreciation (for a lifetime of n=7 years). Which one is the preferred method for tax purpose at MARR of 10% per year? (25pts)