MAYBE
0.08/0.18	MAYBE
0.08/0.18	
0.08/0.18	Problem:
0.08/0.18	 or(true(),y) -> true()
0.08/0.18	 or(x,true()) -> true()
0.08/0.18	 or(false(),false()) -> false()
0.08/0.18	 mem(x,nil()) -> false()
0.08/0.18	 mem(x,set(y)) -> =(x,y)
0.08/0.18	 mem(x,union(y,z)) -> or(mem(x,y),mem(x,z))
0.08/0.18	
0.08/0.18	Proof:
0.08/0.18	 Open
0.08/0.18	EOF