the following demand during the lead time for BB$-1$:

$\backslash$table$[[$Demand During Lead Time,Probability$],[10,0\mathrm{.}1],[30,0\mathrm{.}2],[50,0\mathrm{.}2],[70,0\mathrm{.}2],[90,0\mathrm{.}2],[110,0\mathrm{.}1]]$

The reorder point for BB$-1$ is $50$ sets. What level of safety stock should be maintained for BB$-1?$

The optimal quantity of safety stock which minimizes expected total cost is $,$ sets $($enter your response as a whole number$).$