Eighty units of product X are needed at the beginning of week 6, and another 30 units are needed at the beginning of week 8. Prepare the material requirements plan for component D, B, and X. D can be ordered only in whole cases (50 units per case). One case of D is automatically received every other week, beginning in week 1 (i.e., week 1, 3, 5, 7). Also, there are 30 units of B and 20 units of D on hand now. Lead times for all items are a function of quantity: one week for up to 100 units, two weeks for 101 to 200 units, three weeks for 201 to 300 units, and four weeks for 301 or more units.