Which of the following statements regarding the production order quantity model is TRUE? It relaxes the assumption that the demand rate is constant. It relaxes the assumption that all the order quantity is received at one time. It minimizes the total production costs. It minimizes inventory. It applies only to items produced in the firm's own production departments. If daily demand is normally distributed with a mean of 15 and standard deviation of 5 , and lear time is constant at 4 days, a 90 percent service level will require how much safety stock? 16 units 10 units 7 units 26 units 13 units