The region consisting of all points in three-dimensional space within 3 units of line segment \overline{A B} has volume 216 \pi. What is the length A B ?

**Answer Choices**

A. 6

B. 12

C. 18

D. 20

E. 24

The region consisting of all points in three-dimensional space within 3 units of line segment \overline{A B} has volume 216 \pi. What is the length A B ?

**Answer Choices**

A. 6

B. 12

C. 18

D. 20

E. 24