Use K = 39, Mn = 55, O = 16. In acidic medium $\mathrm{MnO}{}_4{}^{-}$ is reduced to $\mathrm{Mn}{}^{2+}$. The equivalent mass of $\mathrm{KMnO}{}_4$ in this medium is:

1. A31.6
2. B52.7
3. C158
4. D79.0