please solve showing steps, dont use excel

Problem (3): A manufacturing company has purchased three assets: Item Lathe Initial Cost $55,000 Book Life 12 years MACRS class 7 years Salvage Value $3,000 Book Depreciation DDB Truck $35,000 200,000 miles 5 years $2,000 Unit Production Building $850,000 50 years 39 years $100,000 SL The usage of the truck was 22,000 miles and 25,000 miles in the first two years, respectively. a) Calculate the book depreciation of each asset for the first two years b) If the lathe is to be depreciated over the early portion of its life by DDB method then by a switch to the SL method for the remainder of its life. When should the switch occur