12.4-6.*Consider the following special type of shortest-path problem(see Sec. 9.3) where the nodes are in columns and the only paths considered always move forward one column at a time.
The numbers along the links represent distances, and the objective is to find the shortest path from the origin to the destination.This problem also can be formulated as a BIP model involving both mutually exclusive alternatives and contingent decisions.(a)Formulate this model. Identify the constraints that are for mutually exclusive alternatives and that are for contingent decisions.C(b)Use the computer to solve this problem.