When `KMnO_(4)` is reduced with oxalic acid in acidic solution, the oxidation number of `Mn` changes from

When KMnO_4 is reduced with oxalic acid in acid medium, the oxidation number of Mn changes from :

On reduction of KMnO_(4) by oxalic acid in acidic medium, the oxidation number of Mn. What is the magnitude of is change?

In acidic medium oxidation state of Mn changes from