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

B?????????????168

1???????????????5406;????270??????270?????135

40?????????????????18510;????925;????925;???462

C?????????????105

1???????????????4110;????205;????205;???102

40?????????????????12300;????615;????615;???307

C?????????B????????????140??????????B????????????????

D?????????????60(???????D????)

1?????????????3120;????156;????156;???78

20?????????????5400;????270;????270;???135(???D?????????20??)

D?????????B????????????90?????D??C??40???????????????9000??????450??????450?????225

?????????????D?????????84??20????????????????8430;????421;????421;???211

??????????126????40??????????????????13470;????673;????673;???337

??????????????????????????????????B?????????C??D???????B????????C?????D???????B????

????????A????????????????????Σ???????????A?????????BCD??

??????????????R????СR????????**??????B?????e????B????????????????????

????????????????????????????????????????????????????????????鱦??????????????????????????????????????????鱦?????????????????????????????????????????????????淨(jìng)?????????????????????????

???????????????????????????????????飬??????????????????

??????????辭??=5n^2+5n+1990

????????????=5/6*n*(n+1)*(2n+1)+5/2*(n+1)*n+1990n-2000(n>1???????????1???????)

n=20,????53200????????20???????106.4?1????????107?

n=40,????192400,??????40???????384.8?1????????385?

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