A customer wants an order of $100$ in period $4.$ What can you tell him?

The customer from part $($b$)$ cancels his request, but then says he wants $120$ in period $5.$ What do you tell him now?

Sales has requested that you add an MPS of $200$ in period $9$ to cover their needs for a sales promotion. What do you tell them and why?

What action $($if any$)$ should be taken in period $11?$ Why is it okay to take the action?