A car dealer wishes to see whether his profit is lower than that of his competitor. The competitor profit is $480 per sale. The average profit per sale tabulated for the past 90 days was $368 with a standard deviation of $190.

a) at " alfa " is there sufficient evidence to indicate that the average profit per sale of this car dealer is less than his competitor?

b) Find the 99% confidence interval of the true population mean

please answer with explanation thanks