The standard potentials of the $$\mathrm{MnO_4^-/Mn^{2+}}$$ and $$\mathrm{MnO_2/Mn^{2+}}$$ half cells in acidic medium are $$1.51\ \mathrm V$$ and $$1.23\ \mathrm V$$ respectively at $$298\ \mathrm K$$. The standard potential of the $$\mathrm{MnO_4^-/MnO_2}$$ half-cell in acidic medium at the same temperature is

A

$$5.09\ \mathrm V$$

B

$$1.70\ \mathrm V$$

C

$$0.28\ \mathrm V$$

D

$$3.34\ \mathrm V$$