Can you please explain how this is the answer, please and thank you!

(4) 5 blood samples are drawn from another patient (with unknown population potassium level). The sample mean of these blood samples is I = 4.1mEq/dl. The standard deviation of a blood sample is known to the o = 0.2mEq/dl. Using the normal distribution, construct a 99% confidence interval for their true mean potassium level. (A) [3.92,4.28] [B] [4.62,3.59] [C] [3.71,4.49] [D] [3.77,4.30] E] [3.87,4.32]