safety stock

Scott Stereo orders Dutch brand cassette tapes once every three weeks. Weekly demand for the T-60 format is approximately normal with a mean of 200 units and a standard deviation of 30 units. The tapes cost Scott $0.65 each and sell for $1.25. Lead time for delivery is one week. Scott desires a safety stock that will give the store a cycle service level of 98%. If Scott’s inventory level for the Dutch T-60 tapes is at 230 units when it places an order, determine:
a. The order quantity for the tapes.
b. The desired safety stock.