Hi! I need help with this question please!:) thank you!

It is week 1 and there are currently 20 Xs in stock. We need 300 Xs at the start of week 5. If there are scheduled receipts planned for week 3 and week 4 of 120 Xs each and X has a lead time of 2 weeks, when and how large of an order should be placed to meet the requirement of 300 Xs?

		Week 1, 300 Xs
		Week 3, 40 Xs
		Week 5, 40 Xs
		Week 4, 40 Xs
		Week 4, 300 Xs