?? ??????????????????
????:1?????:?????
2???????vx
3?????sn
4????????
5?????????????
??????????????1????????20???????????? (? ?????)?20?????????,??,???????
??«?????????????(??????????)????»,??????????????????????????????????(??)??3???????????,???6000??????,???15%??,??????1?????????,?500?????
20?,????????????????????????“????,?3999????,????500??,???????????????????480????,?980????,????‘????’?”???
???,???????????,????????,???????????“??”?????????,?????????????????????????????????????????????????“????”?(?????) ??:????