Students run an experiment to determine the rotational inertia of a large spherically shaped object around its center. Through experimental data, the students determine that the mass of the object is distributed radially. They determine that the radius of the object as a function of its mass is given by the equation r=km^2, where k=3m/kg^2. Which of the following is a correct expression for the rotational inertia of the object? Answer choices:
A. m^3
B. 1.8m^5
C. 3.6m^5
D. 6m^5
E. 9m^5