I need help in understanding how the answer of part i) was derived. Mean = 1142.2 and SD = 794.2

Question 1 An engineer produced a 95% confidence interval of (1000.1, 1284.3) for the average number of days until a wind turbine fails based on a sample of 120 turbines. i) Based on this information, calculate the mean and the standard deviation of the sample. (5 marks) Her supervisor has indicated that she does not want the upper estimate to exceed the mean by more than 100 days. ii) How many more samples should the engineer collect in order to meet her supervisor's requirements