Problem N5576 probability theory confidence interval

5576. x̅=10, n=25, σ=8, γ=0.989. Determine the confidence interval for estimating with reliability γ=0.989 the unknown mathematical expectation a of the normally distributed feature X of the general population, if the sample mean x̅в=10, the sample size n=25 and the general standard deviation σ=8 are known.