 For this reason, it is strongly NP-hard and there can be no polynomial time approximation algorithm, which has an approximation ratio smaller than formula_1 unless formula_2.Furthermore, unless formula_2, there cannot be a pseudo-polynomial time algorithm that has an approximation ratio smaller than formula_19, which can be proven by a reduction from the strongly NP-complete 3-partition problem.Note that both lower bounds formula_1 and formula_19 also hold for the case that a rotation of the items by 90 degrees is allowed.