Problem $20-36($Algo$)$

Palin's Muffler Shop has one standard muffler that fits a large variety of cars. The shop wishes to establish a periodic review system to manage inventory of this standard muffler. Use the information in the following table to determine the optimal inventory target level $($or order$-$up$-$to level$).$

a$.$ What is the optimal target level $($order$-$up$-$to level$)?($Use Excel's NORMSINV$()$ function to find the correct critical value for the given $-$level. Do not round intermediate calculations. Round $"z"$ value to $2$ decimal places and final answer to the nearest whole number.$)$

Optimal target level

b$.$ If the service probability requirement is $97$ percent, the optimal target level will: $$

Increase $$

Decrease

Stay the same