I've got two little ones at home...I don't have time to sink my battleship anymore. Besides, I think that's what got me into this mess in the first place...
Sub B could persist with Bat A to everywhere it meets up with the resupply deliver. as quickly as the prisoners are transferred, sink Bat A. If no different deliver is offered on the side of Bat A and it keeps into port, then Sub B could desire to enable it circulate to maintain the Bat B group.