To avoid difficulties with the federal or provincial and local consumer protection agen- cies, a beverage bottler must make reasonably certain that 355 millilitre (mL) bottles actually contain 355 mL of beverage. To determine whether a bottling machine is working satisfactorily, one bottler randomly samples 10 bottles per hour and measures the amount of beverage in each bottle. The mean x of the 10 fill measurements is used to decide whether to readjust the amount of beverage delivered per bottle by the filling machine. If records show that the amount of fill per bottle is normally distributed, with a standard deviation of 5.91 mL, and if the bottling machine is set to produce a mean fill per bottle of 357.8 mL, what is the approximate probability that the sample mean of the 10 test bottles is less than 355 mL?