Since the residual values and useful lives of plant: assets are only estimates, it is not uncommon for plant assets to be sold at prices which differ from their book value at the date of disposal.
由于固定资产的残值和使用年限均只是估计，处置固定资产时的出售价格不同于其账面净值是很常见的。
2
When asked to estimate the energy released by this book if it were burned, however, many do have trouble, and the estimates can vary by orders of magnitude.