6. The current controller visits the locations in the to_do list sequentially.

(a) Change the controller so that it is opportunistic; when it selects the next location to visit, it selects the location that is closest to its current position. It should still visit all the locations.

(b) Give one example of an environment in which the new controller visits all the locations in fewer time steps than the original controller.

(c) Give one example of an environment in which the original controller visits all the locations in fewer time steps than the modified controller.

(d) Change the controller so that, at every step, the agent heads toward whichever target location is closest to its current position.

(e) Can the controller from part

(d) get stuck and never reach a target in an example where the original controller will work? Either give an example in which it gets stuck and explain why it cannot find a solution, or explain why it gets to a goal whenever the original can.