The operations manager of a sugar mill in Chesterville wants to estimate the average size of an order received. An order is measured in the number of pallets shipped from overseas. A random sample of 84 orders from customers had a sample mean value of 121.6 pallets. Assume that the population standard deviation is 20 pallets and that order size is normally distributed. Estimate, with 92% confidence, the mean size of orders received from all the mill's customers.