[经] method of average price at the close of the preceding month
qián yuè mò píng jūn dān jià fǎ ㄑㄧㄢˊ ㄩㄝˋ ㄇㄛˋ ㄆㄧㄥˊ ㄐㄩㄣ ㄉㄢ ㄐㄧㄚˋ ㄈㄚˇ
前月末平均单价法