Depreciation and amortization can be used as both the source of repayment and the operating cost (personal understanding):

1. formula: total cost in operation period = operating cost+depreciation+amortization+interest (+maintaining operating investment)

2. Source: depreciation is the distribution of fixed assets during the operation period, while fixed assets are the engineering cost during the construction period, which is the construction cost estimated or actually spent during the construction period;

3. To tell the truth: depreciation has actually been spent during the construction period, but it is calculated as a cost during the operation period, which can be used for tax deduction and is also part of the profit. It just wears a "depreciation" vest, so the depreciation of wearing a vest can repay the loan, and the same amortization can also be used to repay the loan, but amortization is formed by intangible assets and other assets.