What is the common formula of Turnbull's blue and Prussian blue?

CHEMISTRY · Single correct · CBSE · Chemistry · d- and f-Block Elements · d- and f-Block Elements

Problem

What is the common formula of Turnbull's blue and Prussian blue? (1)

\text{Fe}_3[\text{Fe}(\text{CN})_6]_2

(2)

\text{Fe}_4[\text{Fe}(\text{CN})_6]_3

(3)

\text{KFe}[\text{Fe}(\text{CN})_6]

(4)

\text{KFe}_2[\text{Fe}(\text{CN})_6]