$Fac$ and $Mer$ isomerism is associated with which of the following general formula?

How many pairs of enantiomers are possible for the following complex compound,$[M(AB)(CD)ef]^{n \pm}$ (where $AB, CD$ are unsymmetrical bidentate ligands,and $e, f$ are monodentate ligands)?

An octahedral complex having molecular composition $Co \cdot 5NH_3 \cdot Cl \cdot SO_4$ has two isomers $A$ and $B$. The solution of $A$ gives a white precipitate with $AgNO_3$ solution and the solution of $B$ gives a white precipitate with $BaCl_2$ solution. The type of isomerism exhibited by the complex is,

Geometric isomerism is exhibited by which of the following coordination compounds?

Geometrical isomerism can be shown by

Magnetic moment of $[Cu(NH_3)_4]^{2+}$ ion is (in $B.M.$)