Hi µ = 2450 and σ = 400 the management wants to find two value symmetrically on either side of mean, such that the probability that sales of beer during the month will be between the two values is 0.95 and 0.99 find the required value If I am understanding Your Question as intended:OR 95% ⇒ z = 1.96 x = 2450 ± 400*(1.96) x = 2450 ± 784 99% ⇒ z = 2.576 x = 2450 ± 400*(2.576) x = 2450 ± 1030.4 = CI z = value 90% z =1.645 92% z = 1.751 95% z = 1.96 Invnorm(.975) 2-sided (.95 + .05/2 = .975 ) 98% z = 2.326 99% z = 2.576 Standard Normal Curve: Wish You the Best in your Studies.