A certain tower has a mass of 7.2 million kilograms and a height of 324 meters. Its base is square with a side length of 125 meters. The steel used to make the tower occupies a volume of 930 cubic meters. Air has a density of 1.225 kg per cubic meter. Suppose the tower was contained in a cylinder. Find the mass of the air in the cylinder. (Assume the dimensions of the cylinder minimize the volume. Round your answer to three decimal places.)
I know to find its mass = density x (volume of cylinder - volume of tower) but I just can't get to the right answer.
1252 + 1252 = 31250
Square root of 31250 = 176.776953 (Diameter)
Radius = 88.38834765
Volume of Cylinder = Pi x 88.388347652 x 324 = 7952156.404
Volume of Cylinder (7,952,156.404) - Volume of Tower (5,062,500) = 2,889,656.404
2,889,656.404 x 1.225 (Air density) = Mass of air = 3,539,829.095
However its not the right answer, what am I doing wrong?