Exercise 6.14 (Simple Eulerian Path). Let be given a graph with four nodes

a, b, c and d and edges between a and

b, b and

c, c and

d, d and a as well as b and d.

1 Draw a sketch of this graph.

2 Find a Boolean model for this problem.

3 Find all Eulerian paths.

4 How the graph must change by adding or removing one edge such that the existing Eulerian paths are Eulerian circuits, too.