An item of equipment was purchased on 1 July 2015 at a cost of $625 000. It was estimated to have a useful life of four years and a salvage value at the end of that period of $25 000. 

1. Calculate the depreciation expense that would be charged with respect to this equipment in each of the years ending 30 June 2016, 2017, 2018 and 2019 using: 

a. The straight-line method 

b. The reducing balance method (use 40 per cent rate). 

2. Outline the main factors to be considered in selecting an appropriate depreciation method.