At right is a graph of a periodic function and the line $y=5$. One of the intersection points is $(11.31,5)$.  

1. What is the period of the function?

   Hint (a):

   What is the horizontal distance between the two maximum points shown on the graph?

2. Use the symmetry of the graph to state the coordinates of the intersection labeled as point $B$.

   Hint (b):

   Notice that $x=15$ is in the middle of points $A$ and $B$.

3. What are the coordinates of point $C$?

   Hint (c):

   Notice that $x=5$ is in the middle of points $A$ and $C$.