Walt Company leased a tract of land for 40 years at an agreed annual rental fee of \(\$ 18,000\). The effective date of the lease was July 1, 1998. During the last six months of 1998, Walt constructed a building on the land at a cost of \(\$ 450,000\). The building was placed in operation on January 2, 1999, at which time it was estimated to have a physical life of 50 years. Over what period should the building be depreciated? Why?