12(a) For the complexes $\left[\mathrm{FeF}_{6}\right]^{3-}$ and $\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}$. (i) Show the hybridization using VB(valence bond) theory (ii) Calculate the CFSE (crystal field stabilization energy)
(b)Identify the dark blue complex formed when $\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}$ is treated with $\mathrm{FeSO}_{4}$ and account for the origin of its colour.