Number of bridging CO ligands in [Mn₂(CO)₁₀] is:

The stepwise formation of [Cu(NH₃)₄]²⁺ is given below

$\begin{array}{l}{\mathrm{Cu}}^{2+}+{\mathrm{NH}}_3\stackrel{{\mathrm{K}}_1}{\rightleftarrows }{\left[\mathrm{Cu}\left({\mathrm{NH}}_3\right)\right]}^{2+}\\ {\left[\mathrm{Cu}\left({\mathrm{NH}}_3\right)\right]}^{2+}+{\mathrm{NH}}_3\stackrel{{\mathrm{K}}_2}{\rightleftharpoons }{\left[\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_3\right]}^{2+}\\ {\left[\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_2\right]}^{2+}+{\mathrm{NH}}_3\stackrel{{\mathrm{K}}_3}{\rightleftharpoons }{\left[\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_3\right]}^{2+}\\ {\left[\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_3\right]}^{2+}+\mathrm{NH}\stackrel{{\mathrm{K}}_4}{{}_3\rightleftharpoons }{\left[\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_4\right]}^{2+}\end{array}$

The value of stability constants K₁, K₂, K₃ and K₄ $\text{\hspace{0.17em}are\hspace{0.17em}}{10}^4,1.58\times {10}^3,5\times {10}^2\text{\hspace{0.17em}and\hspace{0.17em}}{10}^2$ respectively. The overall equilibrium constants for the dissociation of $[\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_4]$²⁺ is x × 10^–12. The value of x is ________.

(Rounded off to the nearest integer)

1. 2

2. 4

3. 3

4. 1