Consider a program How diagram as a directed graph in which the diamonds and boxes of the program a re nodes, and the logic How arrows between them a re di.reeled edges. For example, the program in Figure 8.7 can be graphed as shown in Figu.re 8.21. Prove that statement testing of a program is equivalent to finding a path in the graph tha t contains all nodes of the graph. Prove that branch testing is equiva lent to finding the set of paths whose union covers the edges. Finally, prove that path testill!g is equivalent to finding all possible paths through the graph.