Final answer:
The accountant should recalculate the annual depreciation expense based on the remaining life of 10 years and depreciate the remaining book value over this new timeframe.
Step-by-step explanation:
The question asks how an accountant should handle the change in the estimated life of a building for depreciation purposes. Initially, the building was to be depreciated over 50 years, but after 30 years, the remaining life has been revised to 10 years. This means recalculating the annual depreciation expense based on the adjusted remaining life of 10 years and the net book value at the time of the estimation change.