The block diagram for an elevator controller for a building with two floors is shown below. The inputs FB₁ and FB₂ are floor buttons in the elevator. The inputs CALL₁ and CALL₂ are call buttons in the hall. The inputs FS₁ and FS₂ are floor switches that output a 1 when the elevator is at the first or second floor landing. Outputs UP and DOWN control the motor, and the elevator is stopped when UP = DOWN 0. N₁ and N₂ are flip-flops that indicate when the elevator is needed on the first or second floor. R₁ and R₂ are signals that reset these flip-flops. DO = 1 causes the door to open, and DC = 1 indicates that the door is closed. Draw an SM chart for the elevator controller (four states).