(b) One example of a greedy algorithm is the Dijkstra algorithm for finding the lowest cost path through a weighted graph. The diagram below shows two weighted graphs that a student wants to investigate using Dijkstra's algorithm. In each case the task it to find the lowest cost of reaching every node from v1. Each graph has a single negative weight in it. V 10 10 15 30 V1 V4 12 -9 8 -7 V3 V3 Graph (a) Graph (b) One of the graphs will yield a correct analysis of the lowest cost for all vertices, and the other will produce an incorrect analysis. Which of the two graphs will produce the incorrect analysis, and explain why the greedy nature of Dijkstra's algorithm is responsible for the incorrect analysis. Your answer should include the key concept of an invariant