YES O(n^5) TRS: { c() -> d(), f(f(X)) -> c(), h(X) -> c()} DUP: We consider a non-duplicating system. Trs: { c() -> d(), f(f(X)) -> c(), h(X) -> c()} Matrix Interpretation: Interpretation class: triangular [X4] [1 0 2 2 2][X4] [2] [X3] [0 0 0 0 0][X3] [0] [h]([X2]) = [0 0 0 0 0][X2] + [0] [X1] [0 0 0 0 0][X1] [0] [X0] [0 0 0 0 0][X0] [0] [0] [0] [d] = [0] [0] [0] [X4] [1 2 0 0 2][X4] [0] [X3] [0 1 0 0 0][X3] [0] [f]([X2]) = [0 0 0 0 0][X2] + [0] [X1] [0 0 0 0 0][X1] [0] [X0] [0 0 0 0 0][X0] [2] [1] [0] [c] = [0] [0] [0] Qed