MAYBE
31.06/10.18	MAYBE
31.06/10.18	
31.06/10.18	Problem:
31.06/10.18	 a(x1) -> x1
31.06/10.18	 a(a(x1)) -> b(b(c(x1)))
31.06/10.18	 c(x1) -> x1
31.06/10.18	 c(b(x1)) -> b(c(a(x1)))
31.06/10.18	
31.06/10.18	Proof:
31.06/10.18	 Open
31.06/10.18	EOF