What is Node and Edge Betweenness in Star Network?

[yecko]

Homework Statement

see image

Relevant Equations

average path length = path length/number of paths
diameter=max path length
average cluster coefficient= interconnection of nodes that connect with one node
average degree = average number of connections per node
core value of each node= 2 if the node exist in a loop, 1 if not in loop
core value of whole network = 2 there exist a loop, 1 if no loop
node betweenness of node 0, and edge betweenness of edge e01= ???

What is "node betweenness of node 0", and" edge betweenness of edge e01" in the question = ?
What is B there in the solution?
why e34 calculated instead of e01?

(as highlighted)

Thank you