Consider a house with two rooms, which we call "left room" and "right room", respectively. We have a robot that is first located in the room on the left. This robot can move between two rooms. We now have 3 red spheres and 3 blue sphere in the room on the left. Our goal is to move all the items to the room on the right by the robot. Unfortunately, the robot can carry a maximum of two balls at a time. Another limiting rule is that the number of red spheres carried by the robot should not exceed the number of blue spheres. We define the state of each moment of the system as follows: (Robot presence/absence in the left room, number of blue balls in the left room, number of red balls in the left room) According to the above description, at the beginning of the system, the state is (1, 3, 3). At the end, the state should be (0, 0, 0). That is, there seems to be nothing in the room on the left and the robot is in the room on the right. Suppose a robot consumes 3 joules of energy per pass. a) What are the actions in this problem? b) What is the cost of the route? c) Write the solution path set? d) What is the total energy consumed by the robot at the end of the work?