Can you please help explain these questions step-by-step? And how to do it on the TI 83?

A) If n=14, "xx (x-bar)=35, and s=6, construct a confidence interval at a 80% confidence level. Assume the data came from a normally distributed population. Give your answers to one decimal place. Submit QuestionQuestion 1 B) You intend to estimate a population mean with a confidence interval. You believe the population to have a normal distribution. Your sample size is 15. Find the critical value that corresponds to a confidence level of 99% (Report answer accurate to three decimal places with appropriate rounding.) Can = to