Answer:
a. The true cost of something in its cost of opportunity
Explanation:
Opportunity cost is the cost which is defined as the cost or expense of one item which is lost in order to get the opportunity to do or to consume something else. In simple words, it is the value or the cost of the next best available alternative.
So, when the person select to bought the textbooks through Chegg instead paying the higher price for the same books through the bookstore. Under this situation, the principle applies is the cost of something in its opportunity cost.
