A complex is represented as ${\mathrm{CoCl}}_{3}x{\mathrm{NH}}_{3^{-}}$ lts 0.1 molal solution in water shows $-{\mathrm{\Delta T}}_{\mathrm{f}}=0.558\mathrm{K}.{\mathrm{K}}_{\mathrm{f}}$ for $H_2\mathrm{O}$ is 1.86 K molality${ }^{-1}$ . Assuming 100% ionization of complex and co-ordination number of Co is six, calculate formula of complex.