The concentration of carbon monoxide (CO) in a gas sample is measured by a spectrophotometer and found to be \(85 \mathrm{ppm}\). Through long experience with this instrument, it is believed that its measurements are unbiased and normally distributed, with population standard deviation \(8 \mathrm{ppm}\). Find a \(95 \%\) confidence interval for the concentration of \(\mathrm{CO}\) in this sample.