Coordination Compounds

The number of isoelectronic species among $Sc^{3+}, Cr^{2+}, Mn^{3+}, Co^{3+}$ and $Fe^{3+}$ is ‘n’. If ‘n’ moles of AgCl is formed during the reaction of complex with formula $CoCl_3(en)_2NH_3$ with excess of $AgNO_3$ solution, then the number of electrons present in the $t_{2g}$ orbital of the complex is ________.