A manager is concerned about their delivery time. You are hired by the manager to find out whether their delivery time is longer than 3.5 days. A random sample of 25 customers is taken. The average delivery time in the sample was 4 days with a sample standard deviation of 1.2 days. Suppose the delivery times are normally distributed.
a) Write down your hypotheses and test the hypothesis at the significance level α=0.05.
b) Compute P-value based on your sample.
c) Write down 95% confidence interval for the mean delivery time.
Please show work