Using the algorithm in the text for finding the minimal spanning tree, which will be the next node added to the set of connected nodes?

Using the algorithm in the text for finding the minimal spanning tree, which will be the next node added to the set of connected nodes? Consider a path 1-2-4-6, in a network where 1 is the source and 6 is the sink. In the iterations of the maximal flow algorithm, the sum of the capacity/flow values of at each end of an arc is always equal to the sum of the original capacity values at each end of the arc. Using the data on a network of oil pipelines from Baku in Azerbaijan to a refinery in Turkey, if we solve the network flow problem with Baku as the source node and the Turkish refinery as the sink node, using the shortest route problem, the algorithm will find all shortest paths from any node to any node. What is the total distance corresponding to the minimal spanning tree of Figure 3a?