Please show me how to find a confidence interval.

(3 points) The Highway Safety Department wants to study the driving habits of individuals. A sample of 26 cars traveling on a particular stretch of highway revealed an average speed of 69.1 miles per hour with a standard deviation of 9.1 miles per hour. Round to 4 decimal places. 1.Calcu|ate a 95% confidence interval for the true mean speed of all cars on this particular stretch of highway. ( , ) 2. What sample size is needed to estimate the true average speed to with in 2.5 mph at 95% confidence? Note: For consistency's sake. round your t* value to 3 decimal places before calculating the necessary sample size. Choose n =