please I cannot figure out question 14.5 thanks

.. 14.3 The demand for subassembly S is 100 units in week 7. Each unit of S requires 1 unit of T and 2 units of U. Each unit of T requires 1 unit of V, 2 units of W, and 1 unit of X. Finally, each unit of U requires 2 units of Y and 3 units of Z. One firm manu- factures all items. It takes 2 weeks to make S, 1 week to make T, 2 weeks to make U, 2 weeks to make V, 3 weeks to make W, 1 week to make X, 2 weeks to make Y, and 1 week to make Z. a) Construct a product structure. Identify all levels, parents, and components. b) Prepare a time-phased product structure. 14.4 Using the information in Problem 14.3, construct a gross material requirements plan. BX 14.5 Using the information in Problem 14.3, construct a net material requirements plan using the following on-hand inventory. On-Hand Inventory 20 Item Inventory Item S On-Hand w 30 T 20 25 U 40 NX 240 V 30 40 AX