Algorithmics course, please explain thoroughly, I'm trying to understand.

8. (Putting theory to Practice, 20pt - you must do this one!) As I talked in class, machines/programs are to regulate event sequences. In theory, we study various automata (such as finite automata, etc) to accept a regular language. However, in practice, trying to regulate a desired sequence pattern for events is not easy at all. here is a problem that you want to solve. There are two kids A and B and there are two apples c,d on the table. Each kid wants to pick up an apple from the table, holds it for a while, and puts it back to the table. Therefore, there are the following kinds of events: A idles; B idles; A picks up c A picks up d B picks up c B picks up d A puts back c A puts back d; B puts back c B puts back d. Notice that, as usual, we assume the interleaving model: at any moment there is at most one event is happending (e.g., A and B can not pick up apple at the same time - this is not possible in computer science). Intially, A and B holds no apple and the two apples c and d are on the table. I want to regulate the event sequences so that at any time, any kid can not hold two apples. Obviously, you need additional control on how the kids are going to behave. Can you design such a control for the kids