Dunstreet's Department Store would like to develop an inventory ordering policy with a $90$ percent probability of not stocking out. To illustrate your recommended procedure, use as an example the ordering policy for white percale sheets.

Demand for white percale sheets is $3,000$ per year. The store is open $365$ days per year. Every three weeks $(21$ days$)$ inventory is counted and a new order is placed. It takes $6$ days for the sheets to be delivered. Standard deviation of demand for the sheets is two per day. There are currently $110$ sheets on$-$hand.

How many sheets should you order?