2. A self-service elevator in an old four-story building operates solely according to the buttons pushed inside the elevator. That is, a person on the outside cannot call the elevator to the floor he is on. Consequently, the only way to get on the elevator is for someone else to get off at your floor. Of the passengers entering the building at the ground floor and wanting to use the elevator, half go to the second floor, and the other half divide equally between the third and the fourth floors. Passen- gers above the ground floor want to go to the ground floor in 80 percent of the cases. Otherwise, they are equally likely to want to go to the other floors. Formulate the Markov chain for elevator movements. 3. The Air Quality Inda