Basement plumbing rough-in

I'm new to this website and forum. I'm looking for some guidance on what plumbing setup I have in my basement (what goes where) and how to proceed with installing a full bathroom. Ideally, I'd like to have a sink and toilet along the wall and a shower in opposite corner. I'm an avid DIYer but have little plumbing experience. My house was built in 2005 and the builder roughed in the plumbing in basement for a bathroom in a nook area of the basement next to the stairwell. Given the other problems we've had with the house I would not be surprised if the rough-in is not correct. I've attached a rough drawing of the layout with an explanation of each piece below:

"A" is a capped 3" PVC pipe that is 3" off the foundation wall, protrudes up from the slab about 12" and enters the slab with a 45 degree elbow.

"B" is a capped 4" PVC pipe that is 17" on center from the foundation wall, protrudes up from the slab about 12". "B" is 28" on center from "A".

"C" is a capped 2.25" PVC pipe that is 22" on center from the foundation wall, protrudes up about 8". "C" is 42" on center from "B".

"D" is a 3" opening with a slotted cap that is almost flush with the slab floor and is 25" on center from the foundation wall.

"E" is a 4" pipe that has a slotted cap that is recessed down in the pipe about 6" below floor level

Any help is much appreciated!

Interesting.

Are the caps glued on or just press-on test caps?

I'd take the caps off and pour water down "C" and see if there is a trap installed. Hopefully there is. I'm guessing that's for a tub/shower. "B" is probably for a toilet - after a 2x4 wall and drywall it will pretty much be 12" OC from the finished wall.

I would expect there to be a cleanout and a vent in the mix. If you eliminate the trapped fixture as a shower it's at least a start.

Edit - I'm going to guess that "A" is the vent. Don't take anything I say as the gospel though. It's fun figuring these puzzles out.

pipes

D and E could be a two way cleanout, and the others will be whatever the installer intended that they be, but we cannot tell without unplugging the risers and looking down the pipes.

the caps are all glued on. sounds like I need to take them off and check water flow.