To find the constant of proportionality (unit price) for a bag of popcorn at each theater, you need two key pieces of information for each theater: the total cost of the bag of popcorn and the quantity or size of the bag. The unit price is calculated by dividing the total cost by the number of bags or size of the bag.
For example, the formula is:
\[ \text{Unit Price} = \frac{\text{Total Cost}}{\text{Quantity or Size}} \]
Since you haven't provided the actual costs or sizes for the bags of popcorn at each theater, I'm unable to give you exact unit prices. If you can provide those specifics, I can help you calculate the unit prices for the theaters listed.