A metal rod with ends A and B is welded at its middle, C, to a cylindrical drum of diameter 12. The rod touches the ground at A making a 30^\circ angle. The drum starts to roll along AD in the direction of D. How far along AD must the drum roll for B to touch the ground?
Answer Choices
A. \pi
B. 2\pi
C. 3\pi
D. 4\pi
E. 5\pi