Getting better. Be carefull using the "process" I I think you are using work the content of book. Thread versus Process.
Now think about walmart. Do the going to each have priorities and FIFO. It looks you are using words from the book but not in the walmart store.
Now don't get discouraged. I am the same for most all in class. My job is to get a picture of walmart operating and identify piece in the book with concurrency.
Now cashier A and B are this is good. The Cashier is a Thread group not scheduler. The thread group like like you said handle some control. Now, does each teller to the Manager and ask to yell for a price check, or do they pickup the and page someone to price check, or whatever? See ? When communication is easy, then threads are best. when communication is hard then process.
Suppose this a customer at the wants to speak to from the hair salon. The cashier cannot page them. Probably, the cashier calls someone in who then gets with the salon.
Now, there would be a process walmart and a process the hair salon. See how the communication gets a little between processess. Also, see the for each process. Now look at the cashiers, see commonality?