Question 870644
Assuming order matters,


There are 6 choices for slot A
There are 5 choices for slot B
There are 4 choices for slot C
There are 3 choices for slot D
There are 2 choices for slot E
There are 1 choices for slot F


Multiply these choices out: 6*5*4*3*2*1 = 720


There are 720 ways to arrange the books (assuming order matters)