Answer:
a) Marginal cost of waiting is greater than the marginal benefit of being served
Explanation:
For an economic perspective, customer leave a fast food restaurant as they find the marginal cost of waiting is higher than the cost of marginal benefit of being served at restaurant.
Marginal cost: In economics, it is a cost that is incurred for an additional unit of benefit received out of certain action or activity.
Marginal benefit: It is a benefit received for an additional unit of cost incurred during the activity taken place.
Therefore, customer have done analysis on the benefit of waiting in a queue for getting served at restaurant, which he found that marginal cost is greater than the marginal benefit of being served.