Final answer:
The depreciation expense formula for straight line depreciation is (Cost - Residual Value) / Useful life. It calculates the amount of depreciation expense incurred each year.
Step-by-step explanation:
The depreciation expense formula for straight line depreciation is option a. (Cost - Residual Value) / Useful life.
This formula calculates the amount of depreciation expense incurred each year by subtracting the residual value (or salvage value) of the asset from its original cost, and then dividing the result by the useful life of the asset.
For example, if a car has a cost of $20,000, a residual value of $2,000, and a useful life of 5 years, the annual depreciation expense would be ($20,000 - $2,000) / 5 = $3,600.