answer all please

The new office supply discounter, Paper Clips, Etc. (PCE, sells a certain type of ergonomically correct office chair which costs $300. The annual holding cost rate is 40%, annual demand is 900, and the order cost is $20 per order. The lead time is 4 days. Because demand is variable (standard deviation of daily demand is 2.4 chairs. PCE has decided to establish a customer service level of 90% The store is open 300 days per year 1. What is the optimal order quantity? 2. What is the safety stock? 3. What is the reorder point