  Based on the model of interaction between spherically symmetrical expanding
matter and the external medium, we have estimated the parameters of the matter
heated by the shock that was produced in the envelope ejected by the explosion
of a classical nova during its interaction with the stellar wind from the
optical companion. Using this model, we have shown that the matter ejected
during the outburst in the system CI Cam had no steep velocity gradients and
that the reverse shock could heat the ejected matter only to a temperature of
~0.1 keV. Therefore, this matter did not contribute to the mean temperature and
luminosity of the system observed in the energy range 3-20 keV.
