Big Bang question

(I posted this in alt.astronomy, but received no answer)

In the current models of big bang, the inflation period
is followed by a period of re-heating. I have the
following questions about the instant of time when
inflation stopped and re-heating started:

a) what was the diameter of the universe at that point in time?

b) What was the mass of universe at that point in time?

c) What if any was the relation between re-heating and
the growing bubbles?

d) Where does the concept of "dark matter" enter into
this model?