Every three weeks, Salem places an order to replenish the stock of batteries. Weekly demand for batteries follows approximately a normal distribution with a mean of 60 batteries and a standard deviation of 9 batteries. Once an order is submitted, the lead time until receiving the batteries is one week. Salem would like at most a 2% chance of running out of stock during any replenishment period.
1. If there are already 75 batteries in stock, how many should be ordered?
2. What size is the safety stock?