0 QTRS
active(f(X)) → mark(g(h(f(X)))) mark(f(X)) → active(f(mark(X))) mark(g(X)) → active(g(X)) mark(h(X)) → active(h(mark(X))) f(mark(X)) → f(X) f(active(X)) → f(X) g(mark(X)) → g(X) g(active(X)) → g(X) h(mark(X)) → h(X) h(active(X)) → h(X)