Answer:
The $500 is the opportunity cost.
Step-by-step explanation:
The sunk cost can be defined as a cost that has already been incurred. Such as cost can no longer be recovered. A sunk cost is considered to be irrelevant and is excluded from decision making.
If an individual decided to take an accounting course and paid the tuition fee of $500 and gets a job offer later. If he/she decides to take up the job the tuition fee paid will be the sunk cost which cannot be recovered anymore.