Let M and N be two events such that P ( M )=0.6, P ( N )=0.2 and P ( M ∩ N )=0.5, then P ( M^′ / N^′) is

Let M and N be two events such that $\displaystyle \mathrm{P}(\mathrm{M})=0.6, \mathrm{P}(\mathrm{N})=0.2$ and $\displaystyle \mathrm{P}(\mathrm{M} \cap \mathrm{N})=0.5$, then $\displaystyle \mathrm{P}\left(\mathrm{M}^{\prime} / \mathrm{N}^{\prime}\right)$ is