Final answer:
In the equation for the cost of publishing a book, the change in total cost for each book printed is $15, represented by the coefficient of 'x'. The term '1250' is a fixed cost and does not change with the quantity of books.
Step-by-step explanation:
In the equation 15x + 1250 = y, representing the total cost of publishing a book, the change in total cost for each book printed is represented by the coefficient of the variable 'x', which in this case is 15. This means for every additional book printed, the total cost increases by $15. This is because the 15x term represents the variable cost of production, where 'x' is the number of books, and '15' is the marginal cost per book.
The 1250 in the equation represents a fixed cost, which does not change with the number of books printed. It's a one-time cost that occurs regardless of the quantity produced.