Accounting question, depreciation-change in estimate. What am I doing wrong? (quest & calculation inside)?

your book value is wrong. The depreciation wasn't taken for the full 8 years, only 5 of the 8, so it should be 32,000 not 20000. Then (32000-4500)=27500. Divide 27,500 by 5 to get 5500. Pretty sure that is right