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

2?????vx

3?????

4??????????????

5?????????

???????????6???????????21? (??????? ??????)????????,???,?????????????????

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

???,??6??16???,????????,????????????19??30??????????,?,????

6??????????????????????????20?,???,?????????????????????????,???????15??,???????????????????????????????????????????????????????

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

??,???????????????????,????????????,?,???,??,???????????????,?????????????

????????????,???????,????;???????,???????

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

???????????????,???????????????????????30???10????

?????????,??,??????,??????????????(?????????????)

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