What is the concentration of sulfate ion in a 12*mol*L^-1 of Mn(SO_4)_2?

Concentration of $M n {\left(S {O}_{4}\right)}_{2}$ in a $12 \cdot m o l \cdot {L}^{- 1}$ solution? Are you sure it's $M n \left(I V\right)$?
If it is indeed $M n \left(I V\right)$ sulfate, the concentration is $2 \times$ the stated concentration.