Cylinder with largest volume

Given cylinders of equal surface area, fnd the one with largest Volume.

Attempt:

Now I want to use Lagrange multiplier and use the area as a constraint. However, the pi is scaring me. Pi is a constant and so far I have only learnt doing it with variables. I thought of substituting pi with x for example but that is variable. Or should I just treat it as constant and go on with it like this:

.......................... I

........................... II

........................... III

From equation I, h = 2r.

Substituting in III, we get , which is the same as

Now I am stuck here.