Problem
1. Complete the specification of the elevator system given in with a description of the emergency button and its effects.
2. Complete the specification of the elevator system given in by describing the opening and closing of the doors.
3. Modify the specification of the elevator system given in by taking into account the fact that At, the transfer time between two adjacent floors, depends on whether an elevator does or does not stop at a floor. Consider also the case in which the elevator moves from a floor where it is standing.