I'd....
Remove top off Swarm A, place a single sheet of newspaper with a few slits made with a razor knife. Place a medium box on top of that...Open the four frame Nuc and transfer it to that box, placing those 4 frames in the middle of the box with two new frames on each end, making sure to shake all the bees out the Nuc into this box. Place an inner cover with a top entrance on it or just leave the lid slightly propped open for a day or two until you know they've worked their way through the newspaper.....DONE! :)
May the best queen win! :-D