Machinery is purchased on July 1 of the current fiscal year for $240,000. It is expected to have a useful life of 4 years, or 25,000 operating hours, and a residual value of $15,000. Compute the depreciation for the last six months of the current fiscal year ending December 31 by each of the following methods:
(a)straight-line
(b)declining-balance at twice the straight-line rate
(c)units-of-production.