AHSME 1991 Problem 8

Liquid $X$ does not mix with water. Unless obstructed, it spreads out on the surface of water to form a circular film $0.1$cm thick. A rectangular box measuring $6$cm by $3$cm by $12$cm is filled with liquid $X$. Its contents are poured onto a large body of water. What will be the radius, in centimeters, of the resulting circular film? $\text{(A)} \frac{\sqrt{216}}{\pi} \text{(B)} \sqrt{\frac{216}{\pi}} \text{(C)} \sqrt{\frac{2160}{\pi}} \text{(D)} \frac{216}{\pi} \text{(E)} \frac{2160}{\pi}$