MAYBE
21.53/10.18	MAYBE
21.53/10.18	
21.53/10.18	Problem:
21.53/10.18	 f(x,f(y,x)) -> f(f(x,x),f(a(),y))
21.53/10.18	
21.53/10.18	Proof:
21.53/10.18	 Open
21.53/10.19	EOF