Alignment help

[[sh...]]

Hello everyone,

I am attempting to make a program for the sub datum XYZ in this drawing but I cant seem to get it right. How would you go about this? 

[[Sv...]]

To me, it looks like an RPS alignment is required. The circles labeled x1, x2, and x3 suggest this. Are there XYZ coordinates corresponding to x1, x2, and x3 in the drawing below?

[[sh...]]

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There are not so I am assuming it is looking for a plane that recalls those three contact locations. My only issue is when I make a plane out of them it does not look right. I tried an RPS using all three locations in Z and the 4way circle as x and y but then I am unsure of which to select as my 6th selection. So the rps had the 4way(Y datum), which is also X 2, selected as x y z and the other two X areas selected as z but then im a bit stumped on the last selection. I know it should be the Z datum but unsure as to which axis.