which of the following changes woul dbe required by gaap to use the retrospective approach? the company chooses to change the depreciaiton method used from sum of years digits to striaght line, the company chooses to change the iseful life and salveage valu e for all of their ppe, th company chooses to change their method for estimating the allowance for doubtful accounts, or the company chooses to change their inventory cost method from average cost to fifo