1973 AHSME Problem 32

The volume of a pyramid whose base is an equilateral triangle of side length 6 and whose other edges are each of length \sqrt{15} is

\textbf{(A)}\ 9 \qquad \textbf{(B)}\ 9/2 \qquad \textbf{(C)}\ 27/2 \qquad \textbf{(D)}\ \frac{9\sqrt3}{2} \qquad \textbf{(E)}\ \text{none of these}

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.