$3.92g$ of ferrous ammonium sulphate crystals are dissolved in 100ml of water.20ml of this solution requires 18ml of potassium permanganate during titration for complete oxidation .The weight of $KMnO_4$ present in one litre of the solution is

Question

$\begin{array}{1 1}(a)\;34.76g&(b)\;12.38g\\(c)\;1.238g&(d)\;3.476g\end{array}$