Consider a long straight road with n buildings scattered sparsely along its length. Let x1 < x2 < . . . < xn denote the locations of these buildings, measured in meters from the left endpoint of the road. Design a greedy algorithm that will place the minimum number of cell towers along this road so that every building is within four miles of one of the towers. Explain your algorithm on a figure, provide pseudocode and state its asymptotic running time. Prove that your greedy algorithm is correct.