Develop a UML state machine to specify the dynamic behavior of a door

that can be opened or closed. When it is closed, it can be locked and

unlocked. Notice that you can open or close a door only if the doorway is

cleared.

$(1)$ Use only simple states.

$(2)$ Use a composite state Closed to medel the behavior of the door when

it is closed. The composite state has two  intetnal states: Unlocked and

Locked.