The optimal dual solution show that the dual price (worth per unit) of raw material M (resource 1) is y=.75 (or $750 per ton) , and that of raw material M (resource 2) is y=.5 (or $500 per ton). These results hold true for specific feasibility ranges as we showed in Section 3.6 For resources 3 and 4 , representing the market and demand limits , the dual prices are both zero , which indicates that their associated resources are abundant. Hence , their worth per unit is zero.