The wheels of a wagon can be approximated as the combination of a thin outer hoop of radius rh=0. 155 m and mass 5. 30 kg, and two thin crossed rods of mass 7. 25 kg each. Imagine replacing the wagon wheels with uniform disks that are td=6. 50 cm thick, made out of a material with a density of 5970 kg/m3. If the new wheel is to have the same moment of inertia about its center as the old wheel about its center, what should the radius of the disk (rd) be?.