please explain. not using excel

I. Problems (In all three problems please round to two decimal places) 1. Rand N Investment Corp. has an annual demand of 1,500, ordering costs of $15/order, and inventory carrying costs of 25% of item price. Price is established by the following quantity discount schedule. What should the order quantity be in order to minimize the total annual cost? When we use the quantity discount model, what are the two basics elements to take into consideration? Why? Quantity Price 1 to 499 500 to 999 1,000 to 1,499 1,500 and up $15.00 per unit $14.50 per unit $14.00 per unit $13.75 per unit