please help me understand these 3 problems with the work and answer provided :)

1. It is week 1 and there are currently 10 As in stock. We need 300 As at the start of week 5 . If there are scheduled receipts planned for week 3 and week 4 of 120 As each and A has a lead time of 2 week, when and how large of an order should be placed to meet the requirement of 300 As? A. Week 1, 300 As B. Week 3,300 AS C. Week 1,50 As D. Week 5,50 As E. Week 3, 50 As 2. An order for 50 units of Product A and 60 of B has been placed. There are currently 25 units of Product B on hand. Each A requires 2 units of Part C; each B requires 6 units of C. There are 160 units of C available. What are the net requirements for C ? A. 300 , B. 115 C. 250 D. 150 3. Consider the bill of material for product P and the data given in the following table. The master schedule requirements for P are 70 units in week 6 . Items Q and R are manufactured internally by the firm and use the lot-for-lot lot-sizing rule. Item S is purchased from a local distributor, and has a Fixed Order Quantity of 50 pieces per order. Use a blank matrix to solve for the MRP requirements. order for R's be released? Given this information, when should thel A. At the start of week 2 B. At the start of week 6 C. At the start of week 4