Design an elevator controller for a simple two-floor elevator. On the 1st floor, there is only an up button, and on the 2nd floor, there is only a down button. Within the elevator, there are two buttons: door open and door close. There are sensors that detect the status of door and location of the elevator. (a) Draw a block diagram with all the necessary input and output. State all your assumptions. (b) Draw the state transition diagram using either Moore or Mealy style, and explain the meaning of each state.