P$11.$ Consider Figure $5\mathrm{.}7.$ Suppose there is another router w$,$ connected to router$$y and z$.$ The costs of all links are given as follows: c$($x$,$y$)=4,$ c$($x$,$z$)=50,$c$($y$,$w$)=1,$ c$($z$,$w$)=1,$ c$($y$,$z$)=3.$ Suppose that poisoned reverse is used in$$the distance$-$vector routing algorithm.PROBLEMS $441$

a$.$ When the distance vector routing is stabilized, router w$,$ y$,$ and z inform their

distances to x to each other. What distance values do they tell each other?

b$.$ Now suppose that the link cost between x and y increases to $60.$ Will there be

a count$-$to$-$infinity problem even if poisoned reverse is used? Why or why not?

If there is a count$-$to$-$infinity problem, then how many iterations are needed for

the distance$-$vector routing to reach a stable state again? Justify your answer.

c$.$ How do you modify c$($y$,$z$)$ such that t