A watch repair shop buys batteries for a variety of products. The most frequent battery purchase is for a Y300 with demand of 3,000 per year. The order cost is $15 per order, and the holding cost is $0.50 per battery. Given the following price schedule, calculate the optimal order quantity.
Number of Batteries Price
1-250 $6.00
250-499 $5.50
500-999 $5.00
1000 or more $4.75