Resistance of $0.2\; M$ solution of an electrolyte is $50 \Omega$. The specific conductance of the solution is $1.4 \;S m^{-1}$ . 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 $S \;m^2 mol^{-1}$ is:
