Given the following situations, identify whether the change would require retrospective treatment or prospective treatment?

From FIFO to Average Cost when it is practical to estimate the change

From 3 year useful life to 5 year useful life to depreciate a machine

From percentage of completion to completed contract for revenue

From FIFO to LIFO when it is impractical to estimate change

From double declining balance to straight-line for depreciation

From 3% estimate for bad debts in A/R to 5% estimate for bad debts in A/R