(a) Find a closed-form expression (i.e., one with no summation sign) for \(\mathbb {E}[(X+1)^{-1}]\) when \(X\) is binomial\((n,p)\) with \(n\geq 1\) and \(0<p<1\).
(b) Find a closed-form expression for \(\mathbb {E}[(X+1)^{-1}]\) when \(X\) is Poisson\((\lambda )\) with \(\lambda >0\). You may use the result of part (a) here.