Answer:
The cost of opportunity of one diner meal is  5 gallons.
Explanation:
The cost of opportunity is the alternative that you sacrifice when you choose an option. Â
It represents the benefits that you miss out on when choosing one alternative over another. Â
In this case, the cost of opportunity of one diner meal is the quantity of gallons that you sacrifice.
7 diners = 35 gallons
1 diner = 35*1/7= 5 gallons
The cost of opportunity of one diner meal is  5 gallons.