The d-electronic configuration of [ CoCl_4]^2- in tetrahedral crystal field is e^m t_2^n. Sum of " m " and "number of unpaired electrons" is ____

The d-electronic configuration of $\displaystyle \left[\mathrm{CoCl}_4\right]^{2-}$ in tetrahedral crystal field is $\displaystyle \mathrm{e}^{\mathrm{m}} \mathrm{t}_2{ }^{\mathrm{n}}$. Sum of " m " and "number of unpaired electrons" is $\displaystyle \_\_\_\_$