4: Property Plant & Equipment (6 Marks) Summer Enterprises Ltd. purchased a piece of machinery on May 31, 2020 for $80,000. The estimated useful life is 10 years with a residual value of 8,500. The Company has a December 31 fiscal year end. The machinery produced 150,000 units in 2020 and 325,000 units the following year. Do not use decimals (round to whole numbers). Required: b) Assume the company now uses the units-of-production method to calculate depreciation expense. Calculate the depreciation expense for the December 31, 2021 year end. I Depreciation Expense at December 31, 2021 Calculations: $ c) Assume now that the company uses the double declining balance method to calculate depreciation. Calculate the net book value at December 31, 2020. Net book value at December 31, 2020 = Calculations: $