A three-quarter sector of a circle of radius 4 inches together with its interior can be rolled up to form the lateral surface of a right circular cone by taping together along the two radii shown. What is the volume of the cone in cubic inches?
Answer Choices
A. 3 \pi \sqrt{5}
B. 4 \pi \sqrt{3}
C. 3 \pi \sqrt{7}
D. 6 \pi \sqrt{3}
E. 6 \pi \sqrt{7}