QUESTION $12$

Chapter $12,$ problem $24.$

One item a computer store sells $is$ supplied $by$ a vendor who handles only that item. Demand for that item recently changed, and

the store manager must determine when $to$ replenish $it.$ The manager wants a probability $ofat$ least $96$ percent $of$ not having $a$

stockout during lead time. The manager expects demand $to$ average a dozen units a day and have a standard deviation $of$ two

units a day. Lead time $is$ variable, averaging four days with a standard deviation $of$ one day.

What $is$ the right formula $to$ calculate safety stock $in$ this problem?

$SS=\frac{z}{b}ar(LT){}_d$

$SS=z\frac{{}_{LT}}{b}ar(d)$

$SS=z\sqrt[\phantom{2}]{LT}{}_d$

$SS=z\sqrt[\phantom{2}]{LT{}_d^2\frac{+}{b}ar(d{)}^2{}_{LT}^2}$