A tile factory earns money by charging a flat fee for delivery and a sales price of $0.25 per tile. One customer paid a total of $3,000 for 10,000 tiles. The equation y - 3,000 = 0.25(x - 10,000) models the revenue of the tile factory,
where x is the number of tiles and y is the total cost to the customer.
Which function describes the revenue of the tile factory in terms of tiles sold?

What is the flat fee for delivery?