Given a state space and the corresponding transition model of a route planning problem as shown in the below figure, starting from the original city A to reach the goal city E, please list the order to expand the nodes (nodes can be labeled by the state/city of the node data structure) in the derived search tree (not the graph representation of the state space as in the below figure), using the tree search algorithm (with no check on repeated states, i.e., visiting the same city multiple time is allowed) by a uniform-cost search (UCS).

A hint: Please be reminded that UCS performs the goal condition check of a node to conclude the search process when the node is expanded (i.e., when the node is removed from the fringe of a priority queue), but not when the node is first generated (i.e., not when the node is inserted into the fringe list). This is one of the key difference between UCS and BFS.

A E 7 3 3 3 1 B C D 3