A major American car manufacturer claims that its new car model averages 40 mpg. A state consumer protection agency has tested this new car model and has found that the highway gas mileage varies under different conditions, but the average is 37 mpg with a standard deviation of 4 mpg. A sample size of 16 was used. At a 0.01 level of significance, can we conclude that the car manufacturer has overestimated the mean mileage? In other words, is the mean mileage of the new car less than 40 mpg? Show all the five steps of the hypothesis testing. Report and interpret the p-value.