Resistance of 0.2 M solution of an electrolyte is $\;50 \;\Omega\;$.The specific conductance of the solution is $\;1.4\;Sm^{-1}\;$.The resistance of 0.5 M solution of the same electrolyte is 280$\;\Omega\;$.The molar conductivity of 0.5 M solution of the electrolyte in $\;Sm^{2}mol^{-1}\;$ is :

Question

$(a)\;5 \times 10^{-4} \qquad(b)\;5 \times 10^{-3} \qquad(c)\;5 \times 10^{3} \qquad(d)\;5 \times 10^{2} $