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

To minimize the total inventory costs, how many orders per year will there be$?$

A$.40$ orders

B$.30$ orders

C$.50$ orders

D$.20$ orders