“…holds for any H ≤ G whenever G is finite and solvable. Following [4], we say that G satisfies the (µ, λ)-property if (1.2) holds for any H ≤ G. Several classes of non-solvable groups satisfy the (µ, λ)-property, for example all the minimal non-solvable groups (see [4]). However it is known that the (µ, λ)-property does not hold for every finite group.…”