Sanders LLC purchased new packaging equipment with an estimated useful life of five years. The cost of the equipment was $30,000, and the salvage value was estimated to be $3,000 at the end of five years. Compute the annual depreciation expenses through the five-year life of the equipment under each of the following methods of book depreciation: (a) The straight-line method. (b) The double-declining-balance method. (c) If switching to the straight-line method is allowed, when is the optimal time to switch?