consider an unstructured overlay network of A$,$B$,$C$,...$to search a file, node a randomly chooses $2$ nodes b and c as its neighbours and sends a request to b and c$.$ a ask b and c each to choose $2$ nodes from the remaining nodes $($not including a$,$b$,$c$)$ as neighbors and send the request to their selected neighbors once more. howmany nodes the message will reach in average?