Take $\mathrm{Pb}{}_3\mathrm{O}{}_4$ as the mixed oxide $2\mathrm{PbO}\cdot \mathrm{PbO}{}_2$ and $\mathrm{Fe}{}_3\mathrm{O}{}_4$ as $\mathrm{FeO}\cdot \mathrm{Fe}{}_2\mathrm{O}{}_3$. Select ALL correct statements (O = $-2$).

1. A$\mathrm{Pb}{}_3\mathrm{O}{}_4$ has Pb(II) and Pb(IV) in the ratio 2:1
2. B$\mathrm{Fe}{}_3\mathrm{O}{}_4$ has Fe(II) and Fe(III) in the ratio 1:2
3. CThe average oxidation number of Fe in $\mathrm{Fe}{}_3\mathrm{O}{}_4$ is $+8/3$
4. DThe average oxidation number of Pb in $\mathrm{Pb}{}_3\mathrm{O}{}_4$ is $+4/3$