The average demand is $500$ per week. It costs $$50$ to place an order. The weekly inventory cost is $30\%$ of the product cost per unit. The cost of the product depends on the quantity of orders. It is $$0\mathrm{.}035$ when you order less than $2800$ units, $$0\mathrm{.}024$ when you order between $2800$ and $4000$ units, and $$0\mathrm{.}020$ when you order more than $4000$ units. What is your optimal order quantity if you want to order between $2800$ and $4000$ units?

$2800$

$2936$

$3315$

$4000$