The radius is the distance from the center to any point. The distance from (2,1) to (0,1) is of course 2. The general formula for a circle with radius r and center (a,b) is

In our case we get
Answer: -252
Hope this helps!
Pretty sure ( -2,-7) because from -1 you go over one then each y is going down 3 so -4 - 3 is -7
The order of the 3 books does not matter so its the number of combinations of 3 from 45
b is the correct choice