Question 1013447
volume of a cylinder is pi*r^2h
at 5 feet,  it is pi*2.5^2*5=31.25 pi
at 7 feet, it is pi*2.5^2*7=43.75 pi
The difference is 12.5 pi=39.27 cubic feet
That is the volume of the cube.
A side is the cube root of the volume.
3.40 feet is the length of the side.