Every year the city of Montreal14 must remove large quantities of snow from sectors i = 1,

c, 60 of the city. Each sector is assigned to one of sites j = 1,

c, 20 as its primary disposal point. From prior-year history, planners have been able to estimate the expected volume of snowfall fi (in cubic meters) in each sector and the capacity uj (in cubic meters) of each disposal site. They also know the travel distance di,j from each sector to each disposal site. Removal rates also have to be considered. The total of hourly removal rates ri (in m3/hr) associated with sectors assigned to any disposal site must not exceed its receiving rate bj (in m3/hr). Formulate an ILP model to select an assignment that minimizes total distance times volume moved using the decision variables (i = 1,

c, 60; j = 1,

c, 20)

xi,j ! e 1 if sector i is assigned to disposal j 0 otherwise