Answer:
These are required to calculate a depreciation expense on an asset:
1. Depreciation rate - the speed at which an asset becomes obsolete. Some assets depreciate faster than others, for example cars lose value more rapidly than houses.
2. Useful life - is the amount of time that the asset is expected to provide economic benefits for the firm. In the case of a computer, for example, average useful life is around 3 to 5 years depending on the company.
4. Salvage value - this is the residual value that the asset will have once its useful life has run out. A company needs this value to calculate the depreciable amount (which equals initial value - salvage value).