A construction company requires to know how much of additives A and B to use to prepare concrete to be used in a freezing environment (northern location). The concrete mix should contain a minimum concentration of nitrate and sulphate. Additives A and B contribute to yielding the following concentration of nitrate and sulphate. Chemical Contribution Cost Additive type Nitrate Sulphate A 2 4 $6 B 4 3 $3 The concrete requires at least 16% of nitrate and 24% of sulphate. Any excess in either component is beneficial but not required.
Formulate a linear programming optimization model. Solve it using the graphical method combined with some linear algebra calculations if required. What if the price of A drops to $4, is the previous solution still valid?