Consider the following graph.

Run Dijkstra's algorithm on this graph starting at node A$.$ When you may select from among many next candidate nodes, prefer the node whichis alphabetically first. Note that we consider $A$ to be the $1$st node explored.

After the $3$rd node is explored, what is the current upper bound on the distance from A to F$?$

Simply enter a numeric value as your answer.

What is the $6$th node explored? Simply enter a single capital letter as your answer.