At 298 K, the standard reduce potentials are 1.51 V for MnO₄⁻, 1.36 V for Cl₂|Cl⁻, 1.07 V for Br₂|Br⁻, 0.54 V for I₂|I⁻. At pH=3, permangnate is expected to oxidize: (RTF=0.059)

For MnO₄⁻ at pH=3, MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O
Here, [MnO₄⁻] = [Mn²⁺] = 1M since in standard state so,
Ecell = Eocell - 0.0595log(1/[H⁺]⁸)
Ecell = 1.51 - 0.059 × 8/5 × pH
Ecell = 1.51 - 0.2832 = 1.23 V
The reduction potential for MnO₄⁻ is 1.23 V which is higher than the standard reduction potentials 1.07 V and 0.54 V for Br₂|Br⁻ and I₂|I⁻ respectively.