IPv$6$ Tunneling and Encapsulation

Consider the network shown below which contains four IPv$6$ subnets, connected by a mix of IPv$6-$only routers$($shaded blue$),$ IPv$4-$only routers $($shaded red$)$ and dual$-$capable IPv$6/$IPv$4$ routers $($shaded blue with red interfaces to IPv$4$ routers$).$ You might want to review Section $4\mathrm{.}3\mathrm{.}4$ in the textbook before doing this problem.