b$.$ Use the EOQ model with planned shortages to find the approximately optimal order

quantity $Q^{***}$ for XYZ plc$.$

c$.$ Given the tolerated stockout probability, find the optimal reorder point $R^{***}.($Recall that

the sum of two normal distributions $N({}_1,{}_1^2)$ and $N({}_2,{}_2^2)$ is the normal distribution

$N({}_1+{}_2,{}_2^2+{}_2^2).$ You may use the distribution tables attached.$)$