Consider quality control sampling of 25 watt LED lights produced by a given manufacturer. The standard deviation of the population of light lifetimes is σ = 42.39 months. Suppose that we choose an SRS of 318 lights. Calculate the standard deviation of their mean lifetime in months. Then apply the Central Limit Theorem and the 68-95-99.7 Rule to complete the following statement: "about 99.7% of all samples will have its mean within ± ________ months of the true population mean μ ."