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a) (15 pts.) Call Gurobi in Python to code and solve the following VRP model. Download from Yulearn data file* named "Midterm.xls" that contains 11 nodes (one depot and 10 customers) and their "pairwise air distances," which are asymmetric. In the second sheet of the same file you can also find the demands for the customers where the demand for the first customer is given as ?? which should be replaced by the last 2 digits of your student ID (for example if your student ID is 20180701040 the demand for the first customer is 40 and you can replace it in the excel file). Suppose vehicle capacity is 150 units. Node 0 shows depot and each vehicle should start and finish their tours at depot. Report optimal solution (routes) and the total lenghth of the tours. Note that the demand of the customers is not unit demand, but they are provided in the excel file. Sets NsetofNodes{1,,n} Parameters cij distance from customer i to customer j dij demand of customer i K is the number of vehicles Q vehicle capacity Decision variables xij={1,0,ifcustomerjisvisitedaftercustomeriotherwise ui load of vehicle after visiting customer i Model: iNjNj=icijxijjNj=ixij=1iNi=jxij=1jNj=0x0j=KNi=0xi0=Kuiuj+QxijQdjdiuiQxij{0,1}ui0iN,i=0jN,j=0i,jN,i=j,i,j=0iN,i=0i,jNiN b) (15 pts.) Resolve part a by forcing not to visit customer 2 right after customer 3 . c) (15 pts.) Resolve part a by forcing to visit customer 8 right after depot. d) (15 pts.) Resolve part a by forcing to visit customer 7 right after customer 10 . x o a) (15 pts.) Call Gurobi in Python to code and solve the following VRP model. Download from Yulearn data file* named "Midterm.xls" that contains 11 nodes (one depot and 10 customers) and their "pairwise air distances," which are asymmetric. In the second sheet of the same file you can also find the demands for the customers where the demand for the first customer is given as ?? which should be replaced by the last 2 digits of your student ID (for example if your student ID is 20180701040 the demand for the first customer is 40 and you can replace it in the excel file). Suppose vehicle capacity is 150 units. Node 0 shows depot and each vehicle should start and finish their tours at depot. Report optimal solution (routes) and the total lenghth of the tours. Note that the demand of the customers is not unit demand, but they are provided in the excel file. Sets NsetofNodes{1,,n} Parameters cij distance from customer i to customer j dij demand of customer i K is the number of vehicles Q vehicle capacity Decision variables xij={1,0,ifcustomerjisvisitedaftercustomeriotherwise ui load of vehicle after visiting customer i Model: iNjNj=icijxijjNj=ixij=1iNi=jxij=1jNj=0x0j=KNi=0xi0=Kuiuj+QxijQdjdiuiQxij{0,1}ui0iN,i=0jN,j=0i,jN,i=j,i,j=0iN,i=0i,jNiN b) (15 pts.) Resolve part a by forcing not to visit customer 2 right after customer 3 . c) (15 pts.) Resolve part a by forcing to visit customer 8 right after depot. d) (15 pts.) Resolve part a by forcing to visit customer 7 right after customer 10 . x o