Edexcel D2 2004 June — Question 7

Exam BoardEdexcel
ModuleD2 (Decision Mathematics 2)
Year2004
SessionJune
TopicNetwork Flows

7. \begin{figure}[h]
\captionsetup{labelformat=empty} \caption{Figure 1} \includegraphics[alt={},max width=\textwidth]{343fdcef-660e-4e8c-bd9c-a7f929dc668e-3_526_903_1455_575}
\end{figure} Figure 1 shows a capacitated directed network. The number on each arc is its capacity. \begin{figure}[h]
\captionsetup{labelformat=empty} \caption{Figure 2} \includegraphics[alt={},max width=\textwidth]{343fdcef-660e-4e8c-bd9c-a7f929dc668e-3_499_967_2231_548}
\end{figure} Figure 2 shows a feasible initial flow through the same network.
  1. Write down the values of the flow \(x\) and the flow \(y\).
  2. Obtain the value of the initial flow through the network, and explain how you know it is not maximal.
  3. Use this initial flow and the labelling procedure on Diagram 1 below to find a maximum flow through the network. You must list each flow-augmenting route you use, together with its flow. \section*{Diagram 1} \includegraphics[max width=\textwidth, alt={}, center]{343fdcef-660e-4e8c-bd9c-a7f929dc668e-4_1920_1175_742_450}
    d) Show your maximal flow pattern on Diagram 2. \section*{Diagram 2} \includegraphics[max width=\textwidth, alt={}, center]{343fdcef-660e-4e8c-bd9c-a7f929dc668e-5_679_1102_315_479}
    (2)
  4. Prove that your flow is maximal.
    (2)
    (Total 13 marks)