答案是selling price - book value = gain or loss on sale = 2
book value = historical cost - accumulated depreciation

我的问题是，gain or loss on sale是不是应该等于-2啊？
还有historical cost和accumulated depreciation分别应该是多少？如果分别是5和6的话，为什么用change from 2005 to 2006来算？
非常感谢。