MAYBE 0.08/0.16 MAYBE 0.08/0.16 0.08/0.16 Problem: 0.08/0.16 f(x,y) -> f(x,x) 0.08/0.16 f(s(x),y) -> f(y,x) 0.08/0.16 0.08/0.16 Proof: 0.08/0.16 Open 0.08/0.17 EOF