YES(?,O(n^2))
TRS:
 {f(x, g y) -> f(g x, y),
  f(x, a()) -> x}
 DUP: We consider a non-duplicating system.
  Trs:
   {f(x, g y) -> f(g x, y),
    f(x, a()) -> x}
  Matrix Interpretation:
   Interpretation class: triangular
         [3]
   [a] = [0]
   
       [X1]    [1 0][X1]   [0]
   [g]([X0]) = [0 1][X0] + [2]
   
       [X3]  [X1]    [1 0][X3]   [1 2][X1]   [0]
   [f]([X2], [X0]) = [0 1][X2] + [0 1][X0] + [1]
   
   
   Qed