7 [Figure 1, printed on the insert, is provided for use in this question.]
The diagram shows some of the main roads connecting Royton to London. The numbers on the edges represent the travelling times, in minutes, between adjacent towns. David lives in Royton and is planning to travel along some of the roads to a meeting in London.
\includegraphics[max width=\textwidth, alt={}, center]{a1290c22-f28d-42aa-89d5-10d60ca4741c-06_2196_1479_557_310}

1. 1. Use Dijkstra's algorithm on Figure 1 to find the minimum travelling time from Royton to London.
   2. Write down the route corresponding to this minimum travelling time.
2. On a particular day, before David leaves Royton, he knows that the road connecting Walsall and Marston is closed. Find the minimum extra time required to travel from Royton to London on this day. Write down the corresponding route.