Two uniform smooth spheres \(A\) and \(B\) of equal radii have masses \(4 m\) and \(m\) respectively. Sphere \(B\) is at rest on a smooth horizontal surface. Sphere \(A\) is moving on the surface with speed \(u\) and collides directly with sphere \(B\). After the collision, the momentum of \(A\) is three times the momentum of \(B\).

Find the value of the coefficient of restitution \(e\).