2. A 100 hp aircraft engine is expected to run a mean time of 2000 h before needing an overhaul, with a standard deviation of 100 h. The manufacturer tests random samples of 5 engines in each of the major markets where the engine is sold. What is the expected standard deviation of the sample means?(four marks)4. A bakery produces cupcakes with a mean mass of 98 g and a standard deviation of 2 g. A cupcake is measured at random, and found to have a mass of 104 g. Should the baker be concerned? What should be done?(four marks)7. A newspaper survey reports that only 23% of the voters in a town favour construction of a new skateboard park. The survey claims an accuracy of 13.2%, 19 times out of 20. How many voters were surveyed?(five marks)