Lab reagent, 90% confidence interval for true concentration.

Exercise 9.20 presented six measurements of a reagent in which the true concentration of the reagent was uncertain. The sample mean based on these six measurements was 4.9883 mg/dL. The distribution of an infinite number of concentration measurements taken from the solution is assumed to be Normal with μ equal to the true concentration of the solution and σ = 0.2 mg/dL. Calculate a 90% confidence interval for the true concentration of the solution based on the current set of observations. What do you conclude?