2??14??,??????????????????????????3?????????????,???????13????????32?????53????

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

??????,??50??????????,??????????????????,????2.5???????????5?????????????????????????????,?????????

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

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

???:????

“?????????”_????

?? ????????????????????50?

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

2?????v×

3?????vx

4?????????

5??????

2??14??,??????????????????????????3?????????????,???????13????????32?????53????

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

??????,??50??????????,??????????????????,????2.5???????????5?????????????????????????????,?????????

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

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

???:????