Iron filling and water were placed in a 5 L vessel and sealed. The tank was heated to 1000∘C. Upon analysis the tank was found to contain 1.1 g of hydrogen and 42.5 g of water vapour. If the reaction in the tank is represented by
3Fe(s)+4H2O(g)⇌Fe2O4(s)+4H2(g)
the value of equilibrium constant Kc is :