If A and B are two events such that P(A)=1/3, P(B)=1/5 and P(A ∪ B)=1/2, then P(A ∣ B^′)+P(B ∣ A^′) is equal to

If $\displaystyle A$ and $\displaystyle B$ are two events such that $\displaystyle P(A)=\frac{1}{3}, P(B)=\frac{1}{5}$ and $\displaystyle P(A \cup B)=\frac{1}{2}$, then $\displaystyle P\left(A \mid B^{\prime}\right)+P\left(B \mid A^{\prime}\right)$ is equal to