Eskasoni Inc. (Eskasoni) recently replaced the roof on its 32-year-old building. The roofing company guarantees the roof for 15 years and advised Eskasoni's management that the roof should last 25 years with no problems. Eskasoni is depreciating the building on a straight-line basis over 40 years and it is expected that the building will have to be demolished and replaced before it is 45 years old.

Required:
How should Eskasoni depreciate the new roof (method, useful life, and residual value)? Explain your answer fully.