In this paper, we present algorithms for locating the vertices in a tree of \(n\) vertices of positive edge-weighted tree and a positive vertex-weighted tree from which we broadcast multiple messages in a minimum cost. Their complexity is \(O(n^2 \log n)\). It improves a direct recursive approach which gives \(O(n^3)\). In the case where all the weights are equal to one, the complexity is \(O(n)\).