A sphere of radius 451cm and uniform surface charge density

Question

Question: A sphere of radius 4.51cm and uniform surface charge density +12.1 µC/m² exerts an electrostatic force of magnitude 4.50×10² N on a point charge +1.55 µC.

Part A: Find the separation between the point charge and the center of the sphere.

r= ______ m ?

I need help to find the separation between the point charge and the center of the sphere.