A mail-order house uses 16,690 boxes a year. Carrying costs are 60 cents per box a year, and ordering costs are $96. The following price schedule applies. 1,000-1,999 $1.25/box 2,000-4,999 $1.20/box 5,000-9,999 $1.15/box 10,000 or more $1.10/box Determine the optimal order quantity.