Billy is opening up a new book shop creating customized books for children. He is deciding whether he should create the books in-house or if he should get a subcontractor to produce the books. He knows if he makes them in-house the annual equipment cost is $38,719 with a variable cost of $10 per book. If he chooses to get the books from a subcontractor he will pay no equipment cost, but a variable cost of $15. How many books would Billy have to sell to make the cost of building in-house and subcontracting the same? (Round to the nearest whole number)