link_effiiciency(G)=(m-average_path_length(G))/m where m is the number of links in G.

1.Show that the link efficiency of line is (2*n-4)/(3*(n-1)) where n is the number of node in the network. (Show all your calculation)

2.Show that the link efficiency of ring networks is (3*n-1)/4n where n is the number of node in the network. (Show all your calculation)

To get the link efficiency of line and ring networks, I need to calculate the average_path_length of line and ring network. How can I do it?