In the $($Q$,f)$ model. if there is no variability in lead time, the re$-$order point $($ROP$)$ can be calculated by the following formula:

$($Mean Demand$)*2"($Std$.$ Dev. of Demand$)$

$($Mean Demand$)"($Review Time$)$

$($Mean Dernand$)"($Lead Time$)+z^{**}($Std$.$ Dev. of Demund$)"($Sq$.$ Rt$.$ of Lead Time$)$

EOQ, using Mean Demand