1. A food factory is making a beverage for a customer from mixing two different existing
products A and B. The compositions of A and B and prices ($/L) are given as follows,
Amount (L) in /100 L of A and B
Lime Orange Mango Cost ($/L)
A 3 6 4 5
B 8 4 6 6
The customer requires that there must be at least 4.5 Litres (L) Orange and at least
5 Litres of Mango concentrate per 100 Litres of the beverage respectively, but no more
than 6 Litres of Lime concentrate per 100 Litres of beverage. The customer needs at
least 100 Litres of the beverage per week.
a) Explain why a linear programming model would be suitable for this case study.
[5 marks]
b) Formulate a Linear Programming (LP) model for the factory that minimises the total
cost of producing the beverage while satisfying all constraints.
[10 marks]
c) Use the graphical method to find the optimal solution. Show the feasible region and
the optimal solution on the graph. Annotate all lines on your graph. What is the minimal cost for the product?
[10 marks]
Note: you can use graphical solvers available online but make sure that your graph is
clear, all variables involved are clearly represented and annotated, and each line is clearly
marked and related to the corresponding equation.
d) Is there a range for the cost ($) of A that can be changed without affecting the optimum solution obtained above?