$6.(15$ pts$)$ One would guess that, in Fortune's algorithm, if we were to perform the plane$-$sweep in the opposite direction $($e$.$g$.,\backslash (+$y $\backslash )$ instead of $\backslash (-$y $\backslash )),$ our order of discovery of the Voronoi vertices would be reversed. $($Recall that each Voronoi vertex is discovered during a circle event.$)$ Prove otherwise: Give a counter$-$example set of sites where reversing the direction of the sweep does not simply reverse the order of discovery. Your counter$-$example should be precise enough to argue the main point without any hesitation or ambiguity.