Use the following information x-bar = 50, = 15, n = 90, N = 1,000--to calculate confidence intervals for assuming the sample is from

Use the following information x-bar = 50, σ = 15, n = 90, N = 1,000--to calculate confidence intervals for assuming the sample is from a normal population:
(a) 90 percent confidence;
(b) 95 percent confidence;
(c) 99 percent confidence.