Examine Footnote 9 (Property and Equipment, Net). Notice that accumulated depreciation stood at $870 million and the end of 2006 and at $903 million...

Examine Footnote 9 (Property and Equipment, Net). Notice that accumulated depreciation stood at $870 million and the end of 2006 and at $903 million at year-end 2007. Assume that depreciation expense for 2007 was $100. Explain what must have happened to account for the remainder of the change in the accumulated depreciation account during 2007.