ABC Electronics sells a popular smartphone model. The average daily demand for

this smartphone is $80$ units, with a standard deviation of $150$ units. The lead time to

replenish the smartphone stock is $5$ days. There are $300$ working days in a year. The

holding cost rate is $15\%,$ the item cost is $$400,$ and the ordering cost is $$180$ per

order.

a$.$ Calculate the economic order quantity for the smartphone.

b$.$ Calculate the safety stock required to achieve a $90\%$ service level.

c$.$ Determine the reorder point and explain the best order policy for this smartphone.

What is the average time between orders?

d$.$ If the required service level increases to $95\%,$ what is the new safety stock

required and the reorder point? Compare and discuss the percent change of safety

stock with the percent change of service level.