Given that the chords intersect at the center, you conclude that they both are diameters.
Now, you have that the point p is the intersection point, so it is the center of the circle.
Then, the length of CP is the radius of the circle, and also the lenght of PB is the radius.
So, the length of CP is equal to the length of PB, and it is 8.
Answer: 8.
