Which of the following statements is/are correct?

(a) The stability constant of ${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]}^{3+}$is greater than that of ${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]}^{2+}$because of the crystal field splitting Effect.

(b) Among ${\mathrm{F}}^{-}, {\mathrm{Cl}}^{-}, {\mathrm{Br}}^{-}$ and ${\mathrm{I}}^{-}, {\mathrm{F}}^{-}$ forms more stable complexes due to small size because F is S.F.L.

(c) According to Irving Williama order, stability of +2 oxidation state for 3d transition series follows :

${\mathrm{Mn}}^{\mathrm{II}}<{\mathrm{Fe}}^{\mathrm{II}}<{\mathrm{Co}}^{\mathrm{II}}<{\mathrm{Ni}}^{\mathrm{II}}<{\mathrm{Cu}}^{\mathrm{II}}>{\mathrm{Zn}}^{\mathrm{II}}$

Hence, the correct option is a, b and c.