YES(?,O(n^1))
TRS:
 {f f a() -> c()}
 DUP: We consider a non-duplicating system.
  Trs:
   {f f a() -> c()}
  Natural interpretation:
   Strict:
    {f f a() -> c()}
   Weak:
    {}
   Interpretation class: stronglylinear
   [a] = + 2
   [c] = + 0
   [f](X0) = + 1*X0 + 7
   
   Qed