In order to oxidise a mixture of \( 1 \) mole each of \( \mathrm{FeC_2O_4} \), \( \mathrm{Fe_2(C_2O_4)_3} \), \( \mathrm{FeSO_4} \) and \( \mathrm{Fe_2(SO_4)_3} \) in acidic medium, the number of moles of \( \mathrm{KMnO_4} \) required is:
\( 3 \)
\( 2 \)
\( 5 \)
\( 7 \)
