An atomic adsorption method for determination of copper content in fuels yielded a pooled standard deviation of Spooled = 0.32 μg Cu/ml (s ---> σ). The analysis of oil from a reciprocation aircraft engine showed a copper content of 8.53 μg Cu/mL. Calculate the 90% and 99% confidence intervals of the results if it was based on (a) a single analysis, (b) the mean of four analyses, (c) the mean of 16 analyses.