Please put all the formulas.. please be accurate

Problem 2 You manage a discount clothing outlet and you are assessing the speed of the checkout line. You hope that the cashiers can check out at least 120 customers per hour. If they average fewer than 120 customers you will need to increase staffing. You record the number of customers served for each of 30 random hours for a sample size of 30. You find the sample average customers served per hour is x = 115 and the sample standard deviation is s = 15. a. Test whether the population mean customers served per hour is less than 120 with a 5% significance level. The z-critical value for this test is Za = Zo.05 = 1.645. Show all your steps clearly and illustrate your answer with a graph. b. Explain what is meant by the term "statistically significant". Is the result you obtained in part a statistically significant