A certain assay for serum alanine aminotransferase (ALT) is rather imprecise. The results of repeated assays of a single specimen follow a normal distribution with a mean equal to the ALT concentration for that specimen and standard deviation equal to 4 U/l. Suppose a hospital lab measures many specimens every day, and specimens with reported ALT values of 40 or more are flagged as "unusually high." If a patient's true ALT concentration is 35 U/l, find the probability that his specimen will be flagged as "unusually high" if the reported value is the mean of three independent assays of the same specimen.