Cutter Enterprises purchased equipment for $72,000 on January 1, 2021. The equipment is expected to have a five-year life, run for 18,000 hours and have a residual value of $5,400. The equipment ran for 2,600 hours in 2021 and 3,900 hours in 2022. Calculate 2021 and 2022 depreciation expense and 2021 year-end book value using: 1. Straight-line depreciation 2. Double declining balance depreciation 3. Sum-of-the-years'-digits depreciation 4. Activity based depreciation