Visual comparison between two competitive solutions highlighted with large dots: (a) solution with the minimum total cost and (b) solution with minimum spatial cost. (Note: This is a map and scatter plot matrix of the four variables. Elements in the upper triangular matrix denote the scatter plots of any two variables, and we found that travel cost gradually increases as spatial cost increases or capacity cost decreases. Diagonal entries in the matrix show the histograms of the corresponding variables, and capacity cost can be approximated with a power law-like distribution. Other variables follow a normal or mixed-normal distribution. Elements in the lower triangular matrix are the spatial deployments of any selected solution).