Assertion (A): Each of the sulphur atom in ${\mathrm{S}}_4{\mathrm{O}}_6^{2-}$ has an oxidation number equal to +2.5

Reason (R): Average oxidation number of sulphur in ${\mathrm{S}}_4{\mathrm{O}}_6^{-2}$  is  +2.5

A and R are correct R is the correct explanation of A

A and R are correct R is not the correct explanation of A

A is wrong, but R is correct

A is correct, but R is wrong