[经] average collection period of receivable

yīng shōu zhàng kuǎn píng jūn shōu huí qī ㄧㄥ ㄕㄡ ㄓㄤˋ ㄎㄨㄢˇ ㄆㄧㄥˊ ㄐㄩㄣ ㄕㄡ ㄏㄨㄟˊ ㄑㄧ