MAYBE
Time: 0.014

Problem:
 Equations:
  hAC(hAC(x1,x2),x3) -> hAC(x1,hAC(x2,x3))
  hAC(x1,x2) -> hAC(x2,x1)
  hAC(x1,hAC(x2,x3)) -> hAC(hAC(x1,x2),x3)
  hAC(x2,x1) -> hAC(x1,x2)
 TRS:
  f(f(x)) -> f(g(x))
  g(x) -> hAC(f(x),f(x))

Proof:
 Open