$2.)$ Demand for an item is $20,000$ boxes per month. The holding cost is $20$ percent per year. Each order incurs a fixed cost of $$400.$ The supplier offers an all$-$unit discount pricing scheme with a price of $$\mathrm{.}5$ per box for orders under $30,000$ and a price of $$4\mathrm{.}90$ for all orders of $30,000$ or more. How many boxes should be ordered per replenishment?