YES O(n^4) 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 [X3] [1 0 0 2][X3] [3] [X2] [0 0 0 0][X2] [0] [h]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] [0] [0] [d] = [0] [0] [X3] [1 0 0 0][X3] [3] [X2] [0 0 0 0][X2] [0] [f]([X1]) = [0 0 1 3][X1] + [0] [X0] [0 0 0 1][X0] [0] [1] [0] [c] = [0] [0] Qed