Answer:
The area of the net is not π • 9^2
:P no explanation for u
The answer for the question shown above is: The shape of the cross section is a triangle.
The explanation is shown below:
Imagine that you have a plane that intersect the rectangular pyramid and it passes through its vertex and it is perpendicular to the base of the pyramid, when you look the cut, you will see a triangle as a cross section.
1728 inches hope this helps!
So... hmmm if you check the first picture below, for 2)
we could use the proportions of those small, medium and large similar triangles like

now.. for 3) will be the second picture below