L sac inc. is a handbag producer. it uses an order$-$up$-$to model to manage its inventory of a plastic buckle. the lead time is $3$ weeks. Demand is normally with a mean of $2300$ units per week and a standard deviation of $1300$ units. What is the oder$-$up$-$to level that achieves a target in$-$stock probability of $99\mathrm{.}6\%?$