(a) In relation to property, plant and equipment, define the terms "depreciation", "depreciable amount", "useful life" and "residual value".
(b) On 1 July 2017, a company which prepares financial statements to 30 June each year acquires an item of equipment at a cost of £59,500. The item's useful life is expected to be five years with a residual value of £10,000. Calculate depreciation charges for each of the five years of the item's useful life, using:

• The straight-line method.
• The diminishing balance method (at a rate of 30%).

How should the company choose between these methods?