Galactic restrictions on iron production by various Types of supernovae
  We propose a statistical method for decomposition of contributions to iron
production from various sources: supernovae Type II and the subpopulations of
supernovae Type Ia -- prompt (their progenitors are short-lived stars of ages
less then $\sim$100 Myr) and tardy (whose progenitors are long-lived stars of
ages $>$100 Myr). To do that, we develop a theory of oxygen and iron synthesis
which takes into account the influence of spiral arms on amount of the above
elements synthesized by both the supernovae Type II and prompt supernovae Ia.
We solve this task without of any preliminary suppositions about the ratio
among the portions of iron synthesized by the above sources.
  The relative portion of iron synthesized by tardy supernovae Ia for the
life-time of the Galaxy is $\sim$35 per cent (in the present ISM this portion
is $\sim$50 per cent). Correspondingly, the total portion of iron supplied to
the disc by supernovae Type II and prompt supernovae Ia is $\sim$65 per cent
(in the present ISM this portion is $\sim$50 per cent).
  The above result slightly depends on the adopted mass of oxygen and iron
synthesized during one explosion of supernovae and the shape (bimodal or
smooth) of the so-called Delay Time Distribution function.
  The portions of iron mass distributed between the short-lived supernovae are
usually as follows: depending on the ejected masses of oxygen or iron during
one supernovae Type II event the relative portion of iron, supplied to the
Galactic disc for its age, varies in the range 12 - 32 per cent (in the present
ISM 9-25 per cent); the portion supplied by prompt supernovae Ia to the
Galactic disc is 33 - 53 per cent (in ISM 26 - 42 per cent).
