A large firm has its equipment inventories listed separately by department. From 20 departments in the firm, FIVE were randomly sampled by an auditor. The proportion of inventory items not properly identified is of interest to the auditor. The auditor selects approximately 10% of the equipment due to time constraint. The data are given in the accompanying table. Department Number of equipment items Number of items not properly identified M (2 - 5) 1 2 3 4 5 150 270 90 310 160 2 3 1 1 2 38.44 26.63 2.96 342.99 27.88 a) Identify the sampling method used in this study. Justify your answer. (3 marks) b) Estimate the proportion of inventory items in the firm not properly identified. Hence, calculate the standard error of estimation. (15 marks) c) Calculate a 95% confidence interval for the proportion of inventory items in the firm not properly identified. Interpret your answer. (2 marks)