How much should the 40-oz size cost?

We found this chalkboard menu at a coffee shop recently. The shop had prices for the 12-oz (small), 16-oz (medium) and 20-ounce (large) cappuccinos.  And they will also make you 40-ounce cappuccino but they haven't listed the price. A 40-oz cup of coffee is pretty huge.  What do you think that the price should be? In this task, students have the opportunity to discover and define a linear relationship.

For Adventurer members we have the activity that can be shown as a PowerPoint presentation. And wee also have an editable Word docx and solutions.