Normal automorphisms of a soluble product of abelian groups

Let G be a soluble product of class n ≥ 2 of nontrivial free abelian groups. We prove that the subgroup of all automorphisms of G identical on the last nonunit commutant G(n), coincides with the subgroup of all inner automorphisms corresponding to the elements of G(n). We also show that the subgroup of all normal automorphisms of G coincides with the subgroup of all inner automorphisms.