Answer:
orders should be placed every 11.15 ≈ 11 days
Explanation:
we need to determine the economic order quantity:
EOQ = √[(2 x S x D) / H]
EOQ = √[(2 x $40 x 13,000) / $6.60] = 396.96 ≈ 397 boxes
total number of orders per year = 13,000 / 397 = 32.75 orders per year
number of days between orders = 365 / 32.75 = 11.145 days