On treatment of 100 mL of 0.1 M solution of $CoCl_3.6H_2O$ with excess $AgNO_3$; $1.2 \times 10^{22}$ ions are precipitated. The complex is :

Question

$\begin{array}{1 1} (1)[Co(H_2O)_6]Cl_3 \\ (2)[Co(H_20)_5Cl]Cl_2.H_2O \\ (3) [Co(H_2O)_4Cl_2]Cl.2H_2O \\(4) [Co(H_2O)_3 Cl_3].3H_2O \end{array} $