Arh! Maths, my nemesis! Why must you haunt me so? In my defence, I was surreptitiously reading Beowulf during classes.
I know there are 24 ways to combine A, B, C and D. ...right? From AAAA to DDDD stopping off at ABCD somewhere in the middle. Can you help me name name, gang?
Help me, and I might just tell you what I'm drawing up over here.