b) Since 2006. the Malaysian police enforced lower car speed limits on federal and state roads during festive seasons, from the default 90 kmfh to 80 km/h as preventive measures to reduce accidents during festive season. A random sample of 25 cars' speed were measured. The mean speed of the cars was 82 kmfh with the standard deviation of 8 kmi'h. Assume that the distribution of car speed is approximately normally distributed. i) Suggest an appropriate distribution to estimate the population mean. Give two reasons for your suggested distribution. (3 marks) ii) Construct a 95% condence interval for the mean car speed on federal and state roads during festive seasons. Interpret its meaning. (5 marks) iii) Based on the confidence interval in (ii), can we conclude that the lowered speed limit on federal and state roads are obeyed by the road users during festive season? Justify your answer. (2 marks) iv) A researcher claimed that the standard deviation of car speed on federal and state roads during festive seasons is 6.8kmlh. Test if the standard deviation is significantly different from the claim at 5% significance level