?:7????????? ??7??????8?

??

??2?16????? ?????,??,2??16?????????20??17?20??,????????????????????????????????4~6??????7~8?;??????????????????????????????7?????????8????????

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

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

1????????????????????,???????;

2???????????????????????????????,?????????????????????????;

3??????????,??????????????????????????;

4????????,???

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

?????????

??????:7????????? ??7??????8? ?????

????????