How do I composite render layers in 2.69 using Cycles? I'm using 2.69 Cycles and I have a plane on one render layer and a cube on a second render layer. Also, under Render -> Film, I have Transparent selected so both layers have no background color.

I want the final image to be the cube and the plane, but I can't figure out which nodes to use to do that. 

If I use a Mix node with Factor set to 0.5, the composited image only shows where the plane and cube visually overlap.

How can I get the final composite to show the full cube and the full plane?

Here is the link to the blend file:
https://drive.google.com/file/d/0B_yQeQQ8ImENSmZaOGJMaGhxczQ/edit?usp=sharing

And here is my Compositing screen:
Try using an Alpha Over node (ShiftA>Add node > Color > Alpha Over):