You make a corner weld between two thin uniform rods of mass 1 kg and length 3 m each. In this situation, the two rods are perpendicular to each other. Determine the moment of inertia about an axis perpendicular to the plane of this system and passing through the welding point.

• A. 1 kg•m²
• B. 3 kg•m²
• C. 6 kg•m²
• D. 9 kg•m²

Answer: (C)