  Energy in nuclear matter is, in practice, completely characterized at
different densities and asymmetries, when the density dependencies of symmetry
energy and of energy of symmetric matter are specified. The density dependence
of the symmetry energy at subnormal densities produces mass dependence of
nuclear symmetry coefficient and, thus, can be constrained by that latter
dependence. We deduce values of the mass dependent symmetry coefficients, by
using excitation energies to isobaric analog states. The coefficient
systematic, for intermediate and high masses, is well described in terms of the
symmetry coefficient values of a_a^V=(31.5-33.5) MeV for the volume coefficient
and a_a^S=(9-12) MeV for the surface coefficient. These two further correspond
to the parameter values describing density dependence of symmetry energy, of
L~95 MeV and K_{sym}~25 MeV.
