Two identical uniform rods, each of mass \(M\) and length \(L\), are used to construct two rotating systems. In System 1, two small spheres, each of mass \(m = M/6\), are attached to the opposite ends of the rod. In System 2, the same two spheres are attached to the center of the rod. Both systems are rotated about an axis through the center of the rod and perpendicular to its length. What is the ratio \(I_1 / I_2\) of the rotational inertia of System 1 to the rotational inertia of System 2?