2 The diagram shows an incomplete solution to the problem of using Dijkstra's algorithm to find a shortest path from \(A\) to \(F\). Any cell that has values in it is complete.
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1. (a) Find the missing weight on \(\operatorname { arc } B E\).
   (b) What can you deduce about the missing weight on arc \(C D\) ? You are now given that the weight of arc \(C E\) is not 3 .
2. (a) What can you deduce about the missing weight on arc \(C E\) ?
   (b) Complete the labelling of the boxes at \(E\) and \(F\) on the diagram in the Printed Answer Booklet. [2] Suppose that there are two shortest routes from \(A\) to \(F\).
3. Show how trace back is used to find the shortest routes from \(A\) to \(F\).