A free-style drink dispenser can be controlled so an average of ? mill

A free-style drink dispenser can be controlled so an average of ? milliliters per container is released. Let us state that the ounces of what is released are symmetrically distributed (SD = .40 ml). In this case, what value should the population mean, ?, be controlled at so 6-ml cups will spill over the top only 2% of the time?