Random Extrusion & Cap

Hello. I'm trying to roughly model some buildings onto a terrain I created in Grasshopper, but I'm having some trouble getting the curves to extrude the way I'm looking for. Basically I projected the curves of the building footprints onto my terrain and then I would like to take those curves and extrude them at random varying heights. For some reason the definition I created is creating 5 random values between 10' and 15', but it is only extruding to one of them. Also, because the curves are non-planar, how would I go about capping them?

Thanks in advance!