Center and Spread · Superchallenge problem

A population consists of the four numbers $1, 3, 4, 8$. All $16$ ordered samples of size $2$ are drawn with replacement (for example $(3, 8)$, $(8, 3)$ and $(4, 4)$ are three different samples). For each sample the sample variance $s^2$ (divide by $n - 1 = 1$) is computed. What is the average of these $16$ sample variances?