Response to the following questions:
1. Why is it common to have a gain or loss on the disposal of a long-term operating asset? Is it true that if the useful life and salvage value of an asset could be known with certainty and were realized, there would never be such a gain or loss?
2. When recording the disposal of a long-term operating asset, why is it necessary to debit the accumulated depreciation of the old asset?
If possible, please give examples to better understand your answers.