Each length is 72 times longer so the actual dimensions are 381.6cm by 576 cm
Your average rate of change for the interval is 3/2 or 1.5, so that should be your answer.
Volume of a sphere:
V = 4/3 · r³ π
Diameter: d = 180 ft, r = d/2, r = 90 ft
V = 4/3 · 90³ · 3.14
V = 4/3 · 729,000 · 3.14
V = 3,052,080 ft³
