This is a Binary Integer Linear Problem.
The goal is to minimize the number of supply locations needed to cover a set of demand locations. The time it takes to get from a deman location to a supply location cannot exceed 2 minutes.
Let i ∈ I be the set of demand locations, and j ∈ J be the set of potential supply locations which can potentially cover i ∈ I. Let tij be the travel time between i ∈ I and j ∈ J, and r be the maximal time allowed for travel between i and j. Each i ∈ I is covered only if and only if tij ≤ r. In this problem, i ∈ I must be covered by at least one j ∈ J.
Define the objective function and constraints of this problem.