????:1???????????:???????

2????????

3???????sn

4?????300?3??????

5??????????

6???????30?,??4???,??(??????????“????????”)??10???????????????????,??????????????3???????????????????????,????

???,???????????????“???????”,??????????????????????????,??????????????350??????????,??????,??????

????«???????»“???????”???,?????????????????????????,????????????????????

(?????????????? ????????????? ??????????? ????)

????????:??????????