Case study: Nut supplier
The firm makes four different products from almond nuts grown locally in
Australia: raw nuts (Raw), roasted mixed nuts (Roasted), roasted and salted
mixed nuts (Salted), and chili-coated mixed nuts (Chili). The firm is barely able to
keep up with the increasing demand for these products. However, increasing raw
material prices and foreign competition are forcing the firm to watch its margins
to ensure it is operating in-the most efficient manner possible. To meet
marketing demands for the coming week, the firm needs to produce at least
1,500 kg of the Raw product, between 600 and 700 kg of the Roasted product, at
least 500 kg of the Salted product, and no more than 400 kg of the Chili product.
Each kilogram of the Raw, Roasted, Salted, and Chili product contains,
respectively, 100%, 70%, 55%, and 40% almond nuts with the remaining weight
made up of other nuts. The company has 3000 kg of almond nuts and 1000 kg of
other nuts for use in the next week. The various products are made using four
different machines that hull the nuts, roast the nuts, coat the nuts in chili (if
needed), and package the products. The following table summarises the time
required by each product on each machine. Each machine has 70 hours of time
available in the coming week.
Minutes required per kg
Machine Raw Roasted Salted Chili
Hulling 1.00 1.00 1.00 1.00
Roasting 0.00 1.00 1.75 1.50
Coating 0.00 0.00 0.00 1.00
Packaging 1.50 1.50 1.25 1.00
The controller recently presented management with the following financial
summary of the firm’s average weekly operations over the past quarter.
Product
Raw Roasted Salted Chili Total
Sales Revenue $5,412 $1,846 $623 $1,165 $9,046
Variable Costs
Direct materials $1,331 $560 $144 $320 $2,355
Direct labour $1,092 $400 $96 $130 $1,718
Manufacturing overhead $333 $140 $36 $90 $599
Selling & Administrative $540 $180 $62 $120 $902
Allocated Fixed Costs
Manufacturing overhead $688 $331 $99 $132 $1,250
Selling & Administrative $578 $278 $83 $111 $1,050
Units Sold 1040 500 150 200 1890
1. Formulate an LP model for this problem to maximise the total profit and
briefly describe each equation.
2. Create a spreadsheet model for this problem and solve it using Solver.
3. What is the optimal solution? You must report inputs, output, and
required resources.4. Create a sensitivity report for this solution, and answer the following
questions:
a. If the firm wanted to decrease the production on any product,
which one would you recommend and why?
b. If the firm wanted to increase the production of any product,
which one would you recommend and why?
c. Which resources are preventing the firm from making more
money? If the firm could acquire more of this resource, how much
should it acquire and how much should it be willing to pay to
acquire this resource?
d. If the marketing department wanted to decrease the price of the
Roasted product by $1, would the optimal solution change and
why?