[经] avoidable and unavoidable costs

kě bì miǎn yǔ bù kě bì miǎn chéng běn ㄎㄜˇ ㄅㄧˋ ㄇㄧㄢˇ ㄩˇ ㄅㄨˋ ㄎㄜˇ ㄅㄧˋ ㄇㄧㄢˇ ㄔㄥˊ ㄅㄣˇ