Grain Is Falling from a Chute onto the Ground, Forming $1200 \mathrm { ft } ^ { 3 }$

Multiple Choice

Grain is falling from a chute onto the ground, forming a conical pile whose diameter is always three times its height. How high is the pile (to the nearest hundredth of a foot) when it contains $1200 \mathrm { ft } ^ { 3 }$ of grain?

A) $6.99 \mathrm { ft }$
B) $7.88 \mathrm { ft }$
C) $6.28 \mathrm { ft }$
D) $7.5 \mathrm { ft }$
E) none of these