There are five students: a, b, c, d and e.

There are five kinds of books in the library, namely A, B, C, D and E, and each book has five books.

From a practical point of view, each student can be assigned at least 1 book, which is any one of A, B, C, D and E; There can only be five books, A, B, C, D and E at most, among which there can be no repetition of the same book. This is the rule.

A can you-

1 There are five possibilities: A, B, C, D, E * * *

2 There are five possibilities at this time: AB, AC, AD, AE, BC, BD, BE, CD, CE, DE, *** 10, which is a combination number of two out of five: C, 5, 2=5×4/2! = 10;

3 This time, there are five combinations of 3 =5×4×3/3! = 10, 10 possibilities;

4 times, 5 possibilities;

5 times, 1 possibility;

There are 5+10+10+5+1= 21possibilities to get a grade.

B, C, D and E all give 2 1 possibilities.

Therefore, * * * has 2 1 5 points.