Determine the oxidation number of Carbon in the following: ${\mathrm{C}}_2{\mathrm{H}}_6,{\mathrm{C}}_4{\mathrm{H}}_{10},\mathrm{CO},{\mathrm{CO}}_2$ and ${\mathrm{HCO}}_3^{-}$.

Find out the oxidation number of sulphur in the following species:

${\mathrm{H}}_2{\mathrm{SO}}_4,{\mathrm{S}}_2{{\mathrm{O}}_4}^{2-},{\mathrm{S}}_2{{\mathrm{O}}_7}^{2-},{{\mathrm{HSO}}_3}^{-},{{\mathrm{HSO}}_4}^{-}$