[经] sum-of-the-years'-digits method of depreciation

zhé jiù de nián shù hé jì fǎ ㄓㄜˊ ㄐㄧㄡˋ ㄉㄜ˙ ㄋㄧㄢˊ ㄕㄨˋ ㄏㄜˊ ㄐㄧˋ ㄈㄚˇ