YES
O(n^3)
TRS:
 {f(f(a(), f(x, a())), a()) -> f(a(), f(f(x, a()), a()))}
 DUP: We consider a non-duplicating system.
  Trs:
   {f(f(a(), f(x, a())), a()) -> f(a(), f(f(x, a()), a()))}
  Matrix Interpretation:
   Interpretation class: triangular
         [0]
   [a] = [1]
         [0]
   
       [X5]  [X2]    [1 1 0][X5]   [1 0 0][X2]   [1]
   [f]([X4], [X1]) = [0 1 0][X4] + [0 1 0][X1] + [0]
       [X3]  [X0]    [0 0 0][X3]   [0 0 0][X0]   [0]
   
   
   Qed