A machine that cost $400,000 has an estimated residual value of $40,000 and an estimated useful life of 20,000 machine hours. The company uses units-of-production depreciation and ran the machine 3,000 hours in year 1, 8,000 hours in year 2, 6,000 hours in year 3, and 3,000 hours in year 4. Required:

1. Calculate the machine's depreciable cost.

2. Calculate the amount of depreciation expense that will be taken per each hour the machine is used.

3. Calculate the machine's depreciation expense for each year.

4. Calculate the machine's accumulated depreciation and book value at the end of each year.