The figure below shows 13 circles of radius 1 within a larger circle. All the intersections occur at points of tangency. What is the area of the region, shaded in the figure, inside the larger circle but outside all of the circles of radius 1 ?

**Answer Choices**

A. 4 \pi \sqrt{3}

B. 7 \pi

C. \pi(3 \sqrt{3}+2)

D. 10 \pi(\sqrt{3}-1)

E. \pi(\sqrt{3}+6)