4.

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{6b51f3a0-0945-4254-8c63-20e1371e9e3a-05_812_1655_269_205}
\captionsetup{labelformat=empty}
\caption{Figure 2}
\end{center}
\end{figure}

[The total weight of the network is 293]

Figure 2 models a network of roads. The number on each edge gives the time, in minutes, taken to travel along the corresponding road.
\begin{enumerate}[label=(\alph*)]
\item Use Dijkstra's algorithm to find the shortest time needed to travel from A to J .

State the quickest route.\\
(6)

The road represented by edge GJ is closed due to essential maintenance. Sahil needs to travel along all the other roads to check that they are in good repair. Sahil wishes to complete his route as quickly as possible and will start and finish at the same vertex.
\item Use the route inspection algorithm to find the duration of Sahil's quickest route. State the edges that will need to be traversed twice. You should make your method and working clear.\\
(6)

Given that Sahil will start and finish at vertex C,
\item state the number of times that Sahil will visit vertex E and vertex F in his inspection route.\\
(2)
\end{enumerate}

\hfill \mbox{\textit{Edexcel D1 2018 Q4 [14]}}