Assume S-1 Security Consultants purchased a building for $450,000 and depreciated it on a straight-line basis over 40 years. The estimated residual value was $93,000. After using the building for 20 years, S-1 realized that the building will remain useful only 15 more years. Starting with the 21st year, S-1 began depreciating the building over the newly revised total life of 35 years and decreased the estimated residual value to $15,300. Record depreciation expense on the building for years 20 and 21.