$2.68 \times 10^{-3}$ moles of a solution containing an ion $A^{n+}$ acqired. $1.81 \times 10^{-3}$ moles of $MnO_4^{-}$ for the oxidation of $An^{+} +0 AO_3^{-}$ in acid medium. What is the value of n

Question

$(a)\;3 \\ (b)\;2 \\(c)\;2.5 \\(d)\;3.5$