The real question is thatwe assume of being only one mole, but how do they really know that someone else is a mole since they throw their blame on the others?Like why does Albert accuses Bertie, Bertie accuses Cedric and Cedric denying Bertie's sentence. That would mean that Cedric is the only one who was defending himself while the other two kept on throwing the blame to get rid of accusations.
If I go on Cedric Statement then Bertie's statement becomes nule and the only Valid Answers remain of Albert's and Cedric and that would cover the requirement of "Assuming that moles lie, other agents tell the truth, and there is just one mole among the three"
But.... if we go back on my previous question I'd say that both Albert and Bertieare the moles. Albert blames one of the moles just to get clean and provide more info, while Bertie tries to do the same trick with Cedric, but fails since Cedric is smarter and knows himself not being the mole.