Alan, Ben, Chris, Dave and Emma are eating a big cake. After eating, there was one slice left, and they decided to leave it for Frank but someone ate it! Frank knows that each of these 5 people are each telling one truth and one lie:
It was Emma,
It wasn't Ben.
Ben said: It wasn't Chris, It was Alan.
Chris said: It was Ben, It wasn't Emma.
Dave said: It was Chris, It wasn't Alan.
Emma said: It was Dave, It was Alan.
Who ate the last slice of cake?