In an experiment, 50 mL of 0.1M solution of a salt reacted with 25 mL of 0.1M solution of sodium sulphite. The half equation for the oxidation of sulphite ion is :
${\mathrm{SO}}_3^{2-}\left(aq\right)+{\mathrm{H}}_2\mathrm{O}⟶{\mathrm{SO}}_4^{2-}\left(aq\right)+2{\mathrm{H}}^{+}+2e^{-}$
If the oxidation number of metal in the salt was 3 , what would be the new oxidation number of metal?