The correct order of ${\Delta }_{0 }$ for the following complexes is
$\begin{array}{rl} & {\left[{\mathrm{CrF}}_6\right]}^{3-};{\left[\mathrm{Cr}\right(\mathrm{CN}{)}_6]}^{3-};{\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]}^{3+};{\left[\mathrm{Cr}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{3-}\\ & \begin{array}{llll}\mathrm{P} & \mathrm{Q}& \mathrm{R}& \mathrm{S}\end{array}\end{array}$

CFSE depends on the relative magnitude of crystal field splitting, ${\Delta }_{0 }$ and pairing energy and in turns ${\Delta }_{0 }$depends upon the field produced by ligand and charge on the metal ion. Here, metal and charge present on it is constant i.e. $C{o}^{3+}$. The order of increasing crystal field strength if $F < H_{2}O < N{H}_3 < CN$-. Therefore, CFSE follows the order: Q > R > S > P.