Paragraph: There are n urns each containing (n+1) balls such that...

Paragraph: There are $n$ urns each containing $(n+1)$ balls such that the ith urn contains $i$ white balls and $(n+1-i)$ red balls. Let $u_i$ be the event of selecting ith urn, $i=1,2,3, \ldots, n and W$ denotes the event of getting a white balls.Question: If $n$ is even and $E$ denotes the event of choosing even numbered urn \left(P \left(u_i\right)=\frac{1}{n}\right)$, then the value of$P(W / E) is