4 The network below shows some pathways at a school connecting different departments. The number on each edge represents the time taken, in minutes, to walk along that pathway. Carol, the headteacher, wishes to walk from her office ( \(O\) ) to the Drama department (D) .

1. 1. Use Dijkstra's algorithm on the network to find the minimum walking time from \(O\) to \(D\).
   2. Write down the corresponding route.
2. On another occasion, Carol needs to go from her office to the Business Studies department \(( B )\).
   1. Write down her minimum walking time.
   2. Write down the route corresponding to this minimum time.
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