The radius of a sphere is 6 units. Which expression represents the volume of the sphere in cubic units.
[tex] \frac{3}{4} \pi(6) {}^{2} \\ \\ \frac{4}{3} \pi(6) {}^{3} \\ \\ \frac{3}{4} \pi(12) {}^{2} \\ \\ \frac{4}{3} \pi(12) {}^{3} [/tex]