Can be classified and solved.
(1) 6 people were admitted.
Can be divided into three categories.
① 4+ 1+ 1,C(6,2)*A(3,3)= 15*6=90
② 3+2+ 1,C(6,3)C(3,2)*C( 1, 1)*A(3,3)=360
③ 2+2+2 C(6,2)*C(4,2)*C(2,2)/A(3,3) *A(3,3)=90
There are 540 such cases.
(2) Admission of 5 people.
Choose five people first, c (6,5) = 6.
And then divided into two categories.
① 3+ 1+ 1,C(5,3)*A(3,3)= 10*6=60
② 2+2+ 1,C(5,2)C(3,2)*C( 1, 1)/A(2,2) *A(3,3)=90
In this case, there are 150*6=900 kinds of * *.
(3) admit 4 people.
Choose four people first, c (6,4) =15.
And then divided into one category.
① 2+ 1+ 1,C(4,2)*A(3,3)=6*6=36
In this case, there are 15*36=540 * *.
(4) admit three people.
Choose three people first, c (6,3) = 20.
And then divided into one category.
① 1+ 1+ 1,A(3,3)=6
In this case, * * has 20*6= 120.
Based on the principle of classified counting,
* * * There are 540+900+540+120 = 2100 species.