OCR D2 — Question 5

Exam BoardOCR
ModuleD2 (Decision Mathematics 2)
TopicNetwork Flows

5. The following matrix gives the capacities of the pipes in a system.
To From\(S\)\(T\)\(A\)\(B\)\(C\)D
S--1626--
T------
A----135
B-16---11
C-11----
D-11----
  1. Represent this information as a digraph.
  2. Find the minimum cut, expressing it in the form \(\{ \} \mid \{ \}\), and state its value.
  3. Starting from having no flow in the system, use the labelling procedure to find a maximal flow through the system. You should list each flow-augmenting route you use, together with its flow.
  4. Explain how you know that this flow is maximal.