Use the Empirical Rule
According to the International Tennis Federation (ITF), all competition tennis balls must have a mean mass of 57.7 grams and standard deviation of 0.85 gram.
\\
Suppose a sports complex that receives an order of tennis balls will return any balls for a refund that do not fall within the middle 90% of the ITF mean. What minimum mass (in grams) must the balls have to be designated too great for the sports complex?