need more information on the above

If you know the mean and SD what are the limits of the 95% CI? What is the corresponding width?Q2. A certain normally distributed population has a known s.D of 1. What is the total width of a 95% confidence interval for the population mean?

a. 0.98 b. 1.96 c. 3.92 d. cant be determined from above info.

CB