Answer:
The cost of opportunity is 4 pancakes.
Explanation:
The cost of opportunity is by definition the amount of things you don't do or buy, because of choosing doing or buying something else. In this case, Maria can make:
This means that at every moment, she can choose to make or 8 pancakes or 2 waffles, but not both. If we continue with this logic, in the time she could make 1 waffle, she could have chosen to make 4 pancakes. This is her cost of opportunity.