  We have analyzed pair production in the innermost region of a two-temperature
external soft photon comptonized accretion disk. We have shown that, if the
viscosity parameter is greater than a temperature and r dependent critical
value, the solution to the disk equation is double valued: one, advection
dominated and the other, radiation dominated. When the viscosity parameter is
below this critical value, the accretion rate has to be confined within a
region limited by a minimum and a maximum accretion rates in order to have two
steady state solutions. These critical accretion rates are shown to be
dependent on r, on the temperature and on the viscosity parameter . Depending
on the combination of the parameters, the advection dominated solution may not
be physically consistent.
