A small mail$-$order company uses $15,000$ boxes a year. The holding cost rate is $20$ percent of unit cost per year, and the ordering cost is $$30$ per order. The following quantity discounts are available. Number of Boxes Price per Box $1,000$ to $1,9991\mathrm{.}302,000$ to $4,9991\mathrm{.}205,000$ to $9,9991\mathrm{.}1810,000$ or more $1\mathrm{.}16$ Determine the optimal order quantity. Question $5$ options: $20005000100010000$