Final answer:
A professor's contract with a publisher to write a textbook in exchange for $15,000 after completion is an example of a deferred payment agreement commonly found in the publishing industry.
Step-by-step explanation:
A professor signing a contract with a publisher to write a textbook by Christmas and getting paid $15,000 afterward is an example of a deferred payment agreement. This contractual arrangement stipulates that the author will receive their compensation after they have fulfilled their part of the contract, in this case, the completion of the textbook. Such agreements are quite common in the publishing industry, where authors often receive advances or post-completion payments as part of their remuneration, depending on their negotiation with the publisher. Deferred payment contracts can also include royalty arrangements, where the author might receive ongoing payments based on the sales of the book.