Revolutions about the y-axis: shell method

[Jaina]

Here's the problem I have:
Use the shell method to find the volume of the solid generated by revolving the regions bounded by the lines y=2x, y=x/2, x=1 about the y-axis.

I can't figure out how to get the equations for the height and radius.

 

[Gene]

The height is 2x-x/2
The radius is x