Problem 2: The manager of an auto repair wants to advertise one price for an engine tune-up, with parts included. Before he decides the price to advertise, he needs a good estimate of the average cost of tune-up parts. A sample of 20 customer invoices for tune-ups has been selected and the costs of parts, rounded to the nearest dollar, are listed below. Answer the three questions below.

150, 78, 93, 57, 75, 52, 99, 80, 105, 62

104, 74, 62, 68, 97, 73, 77, 65, 80, 109

1) What is the point estimate for the average cost of all tune-up parts? Answer is 83

2) 99% confidence interval is

I just need the excel function to use with the numbers for question 2, thank you.