Let $E^C$ denote the complement of an event $E$. Let $E_1, E_2$ and $E_3$ be any pairwise independent events with $P\left(E_1\right)>0$ and $P\left(E_1 \cap E_2 \cap E_3\right)=0$.
Then $\mathrm{P}\left(\mathrm{E}_2^{\mathrm{C}} \cap \mathrm{E}_3^{\mathrm{C}} / \mathrm{E}_1\right)$ is equal to :