11. An NC machine is designed to operate properly with power voltage setting between 108 and 112 volts. If the voltage falls outside this range, the machine will stop. The power regulator for the machine can detect variations in increments of one volt. Experience shows that change in voltage take place once every 15 minutes and that within the admissible range (118 to 112 volts), voltage can go up by one volt, stay the same, or go down by one volt, all with equal probabilities.

(a) Express the situation as a Markov chain.