A spherical concave mirror (not parabolic) has a radius of 4 cm on which a ray is incident 3 cm from the principle axis, as shown in the figure. Since the mirror is not parabolic the ray doesn’t pass through the focus. After reflection on A and then on B, the ray crosses the principal axis at point P. Find the distance of P from C.

*The answer should be according to the following convention:

If the ray passes the principle axis left of C the distance is positive, else negative.