Statistics

Let the six numbers \(\mathrm{a_1,a_2,a_3,a_4,a_5,a_6}\), be in A.P. and \(\mathrm{a_1+a_3=10}\). If the mean of these six numbers is \(\frac{19}{2}\) and their variance is \(\sigma^2\), then 8\(\sigma^2\) is equal to :