The moment of inertia of a rod about an axis perpendicular to the rod and passing through one end is ‌
ML2
3
. Two rods are in the X and Y-axis and they both contribute to the moment of inertia about the Z-axis. The rod along the Z-axis does not contribute to the moment of inertia about the Z-axis. Therefore the total moment of inertia of the system is ‌