Question: Dandelin spheres model

Hello.

I am currently working on a geometric proof, that cutting a cone can give you an ellipse. I have chosen the 'Dandelin spheres' proof, but i am having trouble plotting a hollow cone containing two solid spheres of different sizes. 

I thought i could maybe define each function, and then just display th surface area of the revolution of the cone, and the volume of revolution of the spheres in the same plotting table. However, this has proven more difficult than i thought.

f(x):=0.5*x

g(x):=sqrt(0.81-(x-2)^2)

h(x):=sqrt(3.57^2-(x-8)^2)

display([VolumeOfRevolution(f(x), x = 0 .. 10, output = plot, scaling = constrained), VolumeOfRevolution(g(x), x = 0 .. 10, output = plot, scaling = constrained), VolumeOfRevolution(h(x), x = 0 .. 10, output = plot, scaling = constrained)])

(I am aware that i have plotted the cone function (f(x), straight line) as volume and not surface area of revolution)
 

This does not give me one combined plot, but 3 seperate:(

I hope someone has the time to help!
Thank you