Demand for phones at Amazon is $5,000$ per month. The annual holding cost at Amazon is $25$ percent and the company incurs a fixed cost of $$500$ for each order placed. The supplier offers a quantity discount with a price of $$200$ per phone for all orders under $10,000,$ a price of $$195$ for all orders of $10,000$ or more but under $20,000$ and a price of $$190$ for all orders of $20,000$ or more. How many phones should Amazon order per replenishment?