DJ Car Rental wants to estimate the average miles traveled per day by each of its cars rented locally. A random sample of cars is selected with the following results Sample Size =110 Sample Mean = 85.5 miles Sample Standard Deviation = 29.3 miles. 

a. Construct a 90 confidence interval for the average miles traveled per day by each of its cars rented locally 

b. Interpret this interval 

c. How large sample size will need to be selected if we wish to have a 90 confidence interval with a margin for error 10?