Problem 1: Determine which route from the park entrance (O) to station T has the smallest total distance (shortest path problem). Problem 2: How to install phone lines under the roads to establish telephone communication among all the stations in the smallest cost (minimum spanning problem). Problem 3: How to route various trips to maximize the number of trips that can be made per day without violating the limits (maximum flow problem). A 5 2 C B 4 4 3 1 D E 7 T