I don't know how to solve this question.. Could you please help me?

A car owner has just started using a fuel additive which is supposed to give better fuel efficiency, but, is itself costly. She logs the kilometres travelled per $100 spent, and wishes to compare this to her long-term average of 50ka, prior to using the additive. The distances achieved (in kilometres), and their boxplot are below: 510 485 521 506 560 515 491 470 (a) Calculate the sample mean and standard deviation of these data (to hip). [If you are unable to, use the approximate values 510 and 30 in (b).] [2 marks] (b) Calculate a 95% condence interval for the mean distance travelled. Show this on a number line, and use your diagram to show how the condence interval can be interpreted. [4 marks] (c) Use the condence interval to comment on whether or not the additive appears to have changed the distance travelled per $100 spent. [2 marks] (d) What is the major assumption of the condence interval in (b)? Use the boxplot to comment on its validity. [2 marks]