In which of the following order the given complex ions are arranged correctly with respect to their decreasing spin only magnetic moment?

i) ${\left[{\mathrm{FeF}}_6\right]}^{3-}$                

ii) ${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]}^{3+}$

iii) ${\left[{\mathrm{NiCl}}_4\right]}^{2-}$

iv) ${\left[\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_4\right]}^{2+}$