A spherical ball of mass \(m\) is kept at the highest point in the space between two fixed concentric spheres \(A\) and \(B\) . The smaller sphere \(A\) has a radius \(R\) and the space between the two spheres has a width \(d\). The ball has a diameter very slightly less than \(d\) . All surfaces are frictionless. The ball is given a gentle push towards the right . The angle made by the radius vector of the ball with the upward vertical is \(\theta\). What is the total normal reaction force exerted by the spheres on the ball in terms of angle \(\theta\)?