???2??18???????????? (?? ??)????????18??????,???????????????????????????????,??“???”,???????????????,???“??”??,??,??????????????????????

?????“?????”????????????,???????????,?,????????50???(??)??,????????500????,????????????????????????????1-3????????????????,???????0.3%-0.5%/????????????????,?????????????????????????????????????,????????????,?????????????,????????,??

???????,“?”???????????????????????????????,?????????????????,?????,???????????????20??(???????)???????0.3%/???,20???0.5%/????????????????????????????????????

??,??“???????????”???????20???(????????)???,??????????20??????????,??????????????,??????????????????????????????????????????????????(???) ??????:????????????????

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