(c)
From Kohlrausch’s law
$\Lambda_{m}^{\infty} = \ v_{+}\ \lambda_{+}^{\infty} + \ v_{-}\ \lambda_{-}^{\infty}$
For ${CaCl}_{2}$
$\Lambda_{m}^{\infty}({CaCl}_{2})\ \ = \ \Lambda_{Ca^{2 +}}^{\infty} + \ {2\Lambda}_{{Cl}^{-}}^{\infty}$
$= \ 118.88\ \times \ 10^{- 4\ } + \ 2\ \times \ 77.33\ \times \ 10^{- 4}$
$= \ 118.88\ \times \ 10^{- 4}\ \ + \ 154.66\ \times \ 10^{- 4}$
$= \ 273.54\ \times 10^{- 4}\ \ m^{2}\ mho\ {mol}^{- 1}$