public class PurchaseOrderService {
	public float postPurchaseOrder(PurchaseOrder po) {
		Item items[] = order.getItems();
		float total = 0.0f;
		for (int i=0; i<items.length; i++) {
			total=total+items[i].getPrice()*items[i].getQuantity();
		}
		return total;
	}
//...
}