This exercise concerns the problem of planning a route for a robot to take from one city to another. The basic action taken by the robot is ${Go}(x,y)$, which takes it from city $x$ to city $y$ if there is a route between those cities. ${Road}(x, y)$ is true if and only if there is a road connecting cities $x$ and $y$; if there is, then ${Distance}(x, y)$ gives the length of the road. See the map on page romania-distances-figure for an example. The robot begins in Arad and must reach Bucharest.
1. Write a suitable logical description of the initial situation of the robot.
2. Write a suitable logical query whose solutions provide possible paths to the goal.
3. Write a sentence describing the ${Go}$ action.
4. Now suppose that the robot consumes fuel at the rate of .02 gallons per mile. The robot starts with 20 gallons of fuel. Augment your representation to include these considerations.
5. Now suppose some of the cities have gas stations at which the robot can fill its tank. Extend your representation and write all the rules needed to describe gas stations, including the ${Fillup}$ action.