Use the following information and answer questions $($#$13-$#$16)$

University Book Store buys women's polo T$-$shirts from a supplier, which is $$16$ per unit. The store sells $50,000$ T$-$shirts per year. The annual carrying cost of $T-$shirts is $25\%$ of its purchasing price, and the ordering cost is $$40.$ If the book store operates for $250$ days each year, and delivery of an order takes $2$ working days.

How low can the inventory get before the book store places an order?

$200$

$250$

$500$

$400$