In a dendrogram (hierarchical clustering), the distance between nodes is computed using the Ward linkage method. If two clusters $C_1$ and $C_2$ with sizes $n_1=10, n_2=10$ and centroids $\mu_1, \mu_2$ are merged, the distance increases by $\frac{n_1 n_2}{n_1+n_2} ||\mu_1 - \mu_2||^2$. If $|\mu_1 - \mu_2| = 2$, what is the increase in distance?