Two identical solid spheres each of mass \( 2 \, \text{kg} \) and radii \( 10 \, \text{cm} \) are fixed at the ends of a light rod. The separation between the centres of the spheres is \( 40 \, \text{cm} \). The moment of inertia of the system about an axis perpendicular to the rod passing through its middle point is ______ \( \times 10^{-3} \, \text{kg-m}^2 \).
