\(\begin{aligned} & \mathrm{Na}_2 \mathrm{~S}+\mathrm{Na}_2\left[\mathrm{Fe}(\mathrm{CN})_5 \mathrm{NO}\right] \longrightarrow \text A \\ & \text { Sodium nitroprusside } \\ & \end{aligned} \)
The formula of A is :
1. \(Na_4[Fe(CN)_5NOS]\)
2. \(Na_2[Fe(CN)_5NOS]\)
3. \(K_4[Fe(CN)_5NOS]\)
4. \(K_2 [Fe(CN)_4NOS]\)