G Thunberg Inc. were able to buy on the black market a used internal-combustion engine for $8,000 and estimates its useful life is 10 years. Using a $600 salvage value, determine the following:

1. The amount of annual straight-line depreciation. [2]
2. The amount of depreciation for the sixth year computed by the double declining balance method. [4]
3. The amount of depreciation for the sixth year computed by the sum-of-years-digits method. [4]