In late June 2019, the senior accountant at Moving Feast Ltd reviewed the depreciation expenses for the year. He noticed that since 2015, depreciation for a certain class of non-current assets had been calculated on the assumption that there was no residual value. Thus, the depreciation expense for items in this class had been calculated straight-line on cost over 6 years. However, these non-current assets have a significant residual value (estimated at 25% of original cost) and prior to 2015, the residual value was included in calculating the depreciable amount. After further investigation, it was found that the assistant accountant changed the depreciation calculation in 2015 as he found it easier to do the mathematical calculation if he ignored the residual value. The average effect of the change in 2015 was to increase the depreciation expense by $900,000 per year. Assume this amount is material. The senior accountant has directed that depreciation for these items must be calculated using an estimated residual value of 25%. Required: Advise the senior accountant as to whether or not this should be treated as (1) a change in accounting policy; (ii) a change in estimates; and/or (iii) an error. Give reasons for your answer. To answer this question, you will need to explain which one of these it should be treated as (and why) and also why it should not be treated as one of the other types identified. All explanations need to be in your own words