What is partial-year depreciation?

Which formula is used to calculate annual depreciation expense under the straight-line method?

A company purchases equipment for \$24,000 on July 1. The equipment has a useful life of 4 years and a residual value of \$2,000. What is the depreciation expense for the first year using the straight-line method?

A company buys a machine expected to produce 100,000 units over its life. The machine costs \$40,000 and has a residual value of \$4,000. If 8,000 units are produced in the first partial year, what is the depreciation expense for that year using units of production?

A company calculates \$2,400 in partial-year depreciation for a new asset. How should this be reflected in the journal entry and on the balance sheet?