A discrete elevator can sense the following information about its world:

1. What floor the elevator is stopped at.

2. What floors passengers in the elevator want to go to.

3. What floors passengers outside of the elevator want rides from and whether they want to go up or Clown?

4. The status of the elevator door (open or closed).

The elevator is capable of performing the following actions:

1. Go up exactly one floor (unless it is already at the top floor).

2. Go down exactly one flour (unless it is already at the bottom floor).

3. Open the elevator door

4. Close the elevator door.

3. Wait A seconds (a fixed time sufficient for all in the elevator to get off and for all outside the elevator to get in).

Design a production system to control the elevator in an efficient manner. (It is not efficient, for example, to reverse the elevator direction from going up to going down either if there is someone still inside the elevator who wants to go to d higher floor or if there is someone outside the elevator who wants to get on from a higher floor)