I couldn’t figure out how to extrude the ramp from the floor to the top step. I ended up just extruding the vertices at one end of the extruded ramp to make it go all the way from the top to the bottom. However, now I have 2 edges on one side of the ramp which isn’t great…
Ok after viewing the solution, I was able to get it to work 
. The trick was to grab the bottom edge and snap it to the right coordinate using the increment snapping mode.
