?????6??????????17? ??,??6?17????18????????????????

?,6??17??20??18???????20???,???????????????????????,????,????????,?????(250~300?)???????????????(?20~60??,??????????????80??),??????????????

???????????:? ????????:???????? “????????”_????

?? ???????????????

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

2??????

3??????????

4???sn??

5?????

?????6??????????17? ??,??6?17????18????????????????

?,6??17??20??18???????20???,???????????????????????,????,????????,?????(250~300?)???????????????(?20~60??,??????????????80??),??????????????

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