b
\([\mathrm{Pb}(\mathrm{F})(\mathrm{Cl})(\mathrm{Br})(\mathrm{I})]^{2-}\) have three geometrical isomer so formula for \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{\mathrm{n}-6}\) is \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}\) and \(\mathrm{CFSE}\) for this complex is

\(\mathrm{Fe}^{3+} \Rightarrow 3 \mathrm{d}^{5} 4 \mathrm{s}^{\circ}\)

\(\text { Magnetic Moment }=\sqrt{3}\)

\(=1.73 \mathrm{B.M}\)

\(\mathrm{CFSE}=[(-0.4 \times 5)+(0.6 \times 0)] \Delta_{0}\)

\(=-2.0 \Delta_{0}\)