Show that the hypergeometric distribution (H Gleft(k ; n, n_{1+}, n_{+1} ight)) has mean (frac{n_{1+} n_{+1}}{n}) and

Show that the hypergeometric distribution \(H G\left(k ; n, n_{1+}, n_{+1}\right)\) has mean \(\frac{n_{1+} n_{+1}}{n}\) and variance \(\frac{n_{1+} n_{+1} n_{+2} n_{2+}}{n^{2}(n-1)}\).