cplex homework 1

/*********************************************
 * OPL 12.7.0.0 Model
 * Author: Bernd
 * Creation Date: 26.11.2016 at 18:12:32
 *********************************************/

 range warehouses = 1..3;
 range retailers = 1..4;
 int cost[warehouses][retailers] = [[35,30,40,32],[37,40,42,25],[40,15,20,28]];
 int stock[warehouses] = [1200,1000,800];
 int demand[retailers] = [1100,400,750,750];
 dvar float+ transport[warehouses][retailers];
 
 dexpr float obj = sum (w in warehouses, r in retailers)
 	transport[w][r]  * cost[w][r];
 	
 minimize obj;
 
 subject to{
 warehouse01:
 	(sum (r in retailers)
 	   transport[1][r]) <= stock[1];
 warehouse02:
 	(sum (r in retailers)
 	   transport[2][r]) <= stock[2];
 warehouse03:
 	(sum (r in retailers)
 	   transport[3][r]) <= stock[3];
retailer01:
	(sum (w in warehouses)
	  transport[w][1]) == demand[1];
retailer02:
	(sum (w in warehouses)
	  transport[w][2]) == demand[2];
retailer03:
	(sum (w in warehouses)
	  transport[w][3]) == demand[3];
retailer04:
	(sum (w in warehouses)
	  transport[w][4]) == demand[4];
	
 }
 
 execute{
   if(cplex.getCplexStatus() == 1)
   {
     writeln("dual value of constraint 1: ",warehouse01.dual);
     writeln("dual value of constraint 2: ",warehouse02.dual);
     writeln("dual value of constraint 3: ",warehouse03.dual);
   }     
 }