Variations of a result by Dybvig and Ross provide necessary conditions for the FSD, SSD and TSO efficiency of enterprise mixtures. Several of their perfect market portfolio problem results are adapted to the enterprise mixture problem. The results imply that the sets of enterprise mixtures which satisfy the necessary conditions for FSD, SSD and TSO efficiency are unions of finite numbers of convex subsets. Linear programming can be used to determine whether a particular mixture and the (appropriately defined) convex subset to which it belongs satisfy these conditions. These ideas are illustrated by applying them to a simple example.