/// <summary>
        /// Do a volume repack of a set + one of items.
        /// </summary>
        /// <param name="originalItems"></param>
        /// <param name="plusOneItem"></param>
        /// <returns></returns>
        private PackedBoxList DoVolumeRepack(IEnumerable <Item> originalItems, Item plusOneItem)
        {
            var packer = new Packer();

            packer.SetBoxes(this.boxes);
            packer.SetItems(originalItems);
            if (plusOneItem != null)
            {
                packer.AddItem(plusOneItem);
            }

            return(packer.DoVolumePacking());
        }