Q$7$: Demand for the PCPro computer at B$-$Buy is $1,000$ units per month. B$-$Buy incurs a fixed order placement, transportation, and receiving cost of $$4,000$ each time an order is placed. Each computer costs B$-$Buy $$600,$ and the retailer has a holding cost of $10\%.$ The delivery lead time is $6$ days. $($Assume $30$ days in a month.$)$

Describe the optimal inventory system for PCPro explicitly. $($Draw the corresponding inventory$-$time diagram. Explain how the inventory system works, the optimal order amount, the reorder point, and the optimal cost of implementing this system.$)$