If the molar conductivity ${\Lambda }_m$ of a $0.050$ mol L^-1 solution of a monobasic weak acid is $90$ S cm² mol^-1, its extent (degree) of dissociation will be

[Assume ${\Lambda }_{+}^{°}$ = $349.6$ S cm² mol^-1 and ${\Lambda }_{-}^{°}$ = $50.4$ S cm² mol^-1.]