The equation desbribing the total cost is:
This equation has the form:
where m is the slope and b is the y-intercept. Comparing both equations we conclude that in this case we have m=10 and b=1250.
The slope represents the change in cost for each book while the y-intercept represents the intial cost, therefore:
The change in the total cost for eah boog printed is 10.
The cost to get started before any books are printed is 1250.