In this paper we proved the following: 1)Theorem 2. Let G be a gronp, then w_∞(G)=SI(G). 2) Theorem 3. Let G be agroup and N be a normal subgroup of G. If G/N is super-solvable and all prime elements in N are containeb in w_∞(G), then G is supersolvable if and only if T_(2q) is not involved in G.