Group centrality

Considering the group {n₁, n₂, n₃, n₄, n₅, n₇} of the social network in Figure 1, what is the group centrality (using degree centrality as measurement)?

Considering the group {n₁, n₄, n₅, n₆, n₇} of the social network in Figure 1, what is the group centrality (using degree centrality as measurement)?

What does it tell you about the differences between these two groups?

Iigure 1. sorial notwork N={n1,n2,n3,n15}