costs:=Dictionary(
   "W",Dictionary("A",16, "B",16, "C",13, "D",22, "E",17),
   "X",Dictionary("A",14, "B",14, "C",13, "D",19, "E",15),
   "Y",Dictionary("A",19, "B",19, "C",20, "D",23, "E",50),
   "Z",Dictionary("A",50, "B",12, "C",50, "D",15, "E",11)).makeReadOnly();
demand:=Dictionary("A",30, "B",20, "C",70, "D",30, "E",60);  // gonna be modified
supply:=Dictionary("W",50, "X",60, "Y",50, "Z",50);	    // gonna be modified