A company decides to design a lunch box that keeps food cold for students with long bus rides.
The criteria: Keeps food at temperature of less than 4*C
The constraint: Costs less than $6 per box to produce
The designers line three boxes with different amounts of material to determine which is the most effective at reducing energy transfer.
They test the designs by putting a frozen ice pack inside each lunch box along with a thermometer. All of the lunch boxes are placed in a temperature-controlled room at 16*C. An hour later the temperature inside each lunch box is recorded. The results are shown in the image.
Which design best meets the criteria?