Annual demand is constant $2500$ units per year, $250$ working days and lead time averages $8$ days with a standard deviation of $2$ days, $95\%$ does service require how much safety stock? $($Z $=1\mathrm{.}64)$

A$)28$ units

B$)33$ units

C$)141$ units

D$)59$ units

E$)8200$ units