A sample of 29 measurements of radiation levels in a research laboratory taken at random times has a sample mean of x- = 415.7. If an experimenter wishes to use a "known" value a = 10.0 for the standard deviation of these radiation levels based upon prior experience, find the value of C for which μ ∈ (-∞, c) is a one-sided 99% confidence interval for the mean radiation level μ. Is it plausible that the mean radiation level is larger than 418.0?