In back order model, (Q∗−S∗)Cn​=S∗×Cb​S∗=(Ch​+Cb​Q∗Ch​​) Maximum inventory level =(Q∗−S∗)=Q∗−Ch​+Cb​Q∗Ch​​=(Ch​+Cb​Q∗Cb​​)M∗=Ch​2DC0​​×(Cb​Cb​×Ch​​)​×(Ch​+Cb​Cb​​)M∗=Ch​2DC0​​×(Cb​+Cb​Cb​​)​=42×10000×300​×(2925​)​=1137.147 unit ≅1137 units