The molar conductivity of $0.007 \,M$ acetic acid is $20\, S\, cm ^{2} mol ^{-1}$. What is the dissociation constant of acetic acid? Choose the correct option.
$\left[\Lambda_{ H ^{+}}^{\circ}=350 \,S \,cm ^{2} mol ^{-1},
\Lambda_{ CH _{3} COO ^{-}}^{\circ}=50\, S\, cm ^{2} mol ^{-1}\right]$