The circular base of a hemisphere of radius 2 rests on the base of a square pyramid of height 6 . The hemisphere is tangent to the other four faces of the pyramid. What is the edge-length of the base of the pyramid?
Answer Choices
A. 3 \sqrt{2}
B. \dfrac{13}{3}
C. 4 \sqrt{2}
D. 6
E. \dfrac{13}{2}