From the information given in the passage, what is the most likely configuration of the cobalt d-electrons for the species

$\text{ (A) }{\mathrm{CoCl}}_6^{3-}\text{ and (B) }\mathrm{Co}{\left({\mathrm{NO}}_2\right)}_6^{3-}?$

${\mathrm{Cl}}^{\ominus }$ always behaves as weak field ligand so high spin complex formed. Also here $∆$o is not sufficient to overcome pairing energy P, ${\mathrm{NO}}_2^{\mathrm{\Theta }}$ with Co behaves as strong field ligand and hence low spin complex. Also  $∆$o > P and hence pairing takes place.