help pls

a) What is the depreciation expense for yr 20 using the straight-line method? b) What is the net book value of the equipment at the end of year 15 ? c) Calculate gain/loss on sale of equipment. d) What is the account balance in accumulated depreciation at the end of yr 20? c) What is the depreciation expense for yr 1 using the double declining method? f) Assuming the equipment was purchased on June 1, 2020 and sold on 12/31/2025, what is the gain or loss on sale