h.≥0 Xk={x1,x2,…,xk};x∈G d (x,D=min distance between any one pointseX and the noge∈N MIN d(X=.(x,j) x∈XG(N, A), | N |= n hj ≥ 0 hj j =1 n ∑ =1 Xk = {x1, x2 ,..., xk}; x j ∈G d(Xk, j)≡min. distance between any one o points xi ∈Xk and the node j∈N. d(Xk, j)≡ MIN xi ∈Xk d(xi, j)