???????????12???2?????? (????? ????? ??)???12?????????2?????????

??:?,????????????5????????????????????????????,????????????,“??”????,????,?????“??????”?????????

????????:??????????????????????1000????,??????????????????210???,??1520????????????3.7??,68?,?????????????“?????”???“????”?

?“?”?????,?????????????????“?????????”??????????????,????????????????????,??????????????????????????????,??,????????????“??”?,?????????????????????,??“????????????????”?(?) ??:???? ??“????????”????

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

????:1?????????:????v

2?????vx

3???????

4???????

5?????????

???????????12???2?????? (????? ????? ??)???12?????????2?????????

??:?,????????????5????????????????????????????,????????????,“??”????,????,?????“??????”?????????

????????:??????????????????????1000????,??????????????????210???,??1520????????????3.7??,68?,?????????????“?????”???“????”?

?“?”?????,?????????????????“?????????”??????????????,????????????????????,??????????????????????????????,??,????????????“??”?,?????????????????????,??“????????????????”?(?) ??:????