  Cuprate high-Tc superconductors are known to have several relationships
between Tc and features of electronic structure. In the firstly found one, Tc
is correlated with the Madelung potential difference between planar Cu and O
sites. Another one relates Tc to the relative ratio of hole densities at the Cu
and O sites. In this work we analyze the dependences of the strength of
superconductivity (SC) on the model parameters of the d-p model. We first
transform the d-p model into a Hubbard model that proves to have k-dependent
Coulomb interaction. To this model we apply a kind of mean-field theory, i. e.,
Kondo's theory of the d-wave SC gap in cuprates. The obtained so-called SC
strength parameter increases with increase of |ep - ed| on both positive and
negative sides of ep - ed due to increase of effective on-site Coulomb
interaction U. ep and ed are hole energy levels of O2p and Cu3d orbitals
referenced to the d9 configuration. The above-mentioned two relationships are
shown to be understandable in terms of the d-wave SC, if ep - ed < 0.
