Traffic speed: The mean speed for a sample of 40 cars at a certain intersection was 24.80 kilometers per hour with a standard deviation of 2.29 kilometers per hour, and the mean speed for a sample of 141 motorcycles was 39.46 kilometers per hour with a standard deviation of 3.80 kilometers per hour. Construct a 99% confidence interval for the difference between the mean speeds of motorcycles and cars at this intersection. Let u, denote the mean speed of motorcycles and round the answers to at least two decimal places. A 99% confidence interval for the difference between the mean speeds, in kilometers per hour, of motorcycles and cars at this intersection is
