4. Recall that the line graph L(G) of a graph G=(V,E) has a vertex for each edge of G, and two of these vertices are adjacent if and only if the corresponding edges in G have a common end vertex. (a) (7 points) If G is an Eulerian graph, prove that L(G) is also an Eulerian graph. (b) (3 points) Is the converse of the statemenet in part (a) true? Justify your answer!