Inventory control. A computer store sells $7,200$ boxes of storage disks annually. It costs the store $$0\mathrm{.}20$ to store a box of disks for one year. Each time it reorders disks, the store must pay a $$5\mathrm{.}00$ service charge for processing the order. How many times during the year should the store order disks to minimize the total storage and reorder costs?