YES
Time: 0.010

Problem:
 Equations:
  fAC(fAC(x1,x2),x3) -> fAC(x1,fAC(x2,x3))
  fAC(x1,x2) -> fAC(x2,x1)
  fAC(x1,fAC(x2,x3)) -> fAC(fAC(x1,x2),x3)
  fAC(x2,x1) -> fAC(x1,x2)
 TRS:
  fAC(x,one()) -> x
  fAC(x,x) -> x

Proof:
 AC-KBO Processor:
  precedence:
   one ~ fAC
   weight function:
    w0 = 4
    w(one) = 4
    w(fAC) = 0
   problem:
    Equations:
     fAC(fAC(x1,x2),x3) -> fAC(x1,fAC(x2,x3))
     fAC(x1,x2) -> fAC(x2,x1)
     fAC(x1,fAC(x2,x3)) -> fAC(fAC(x1,x2),x3)
     fAC(x2,x1) -> fAC(x1,x2)
    TRS:
     
   Qed