Experiencing major issues in a Electrical Engineering Digital Logic class.

Please help me design a state diagram and synchronous circuit using D Flip-Flop for a simple train station door system.

Input: Train's arrival signal, Human Sensor

Output: Status of Station Door (000: closed, 001: 20% open, 010: 40% open, 011: 60% open, 100: 80% open, 101: open)

- When the train arrives at the station (Arrival Signal), the door opens. - Say Count is 0 at this point. The door remains open for 10. (Door takes 5 to open = 1 to open 20%, and so on) - If nobody is detected for the next 3, door starts to close. - But if somebody is detected within 3, door remains open for 3. This process can be repeated until 20. After 20, the door will start to close.