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A secondary school principal plans to select student volunteers 'om 12 classes to participate in a charity,r activity. 6 student volunteers are selected from each class. Class tutors will use random number generator computer application to randomly select 6 students by their class numbers from each class for joining the charity activity. (a) Identify the sampling method used by the class tutors. (2 marks} (13) State one advantage and one disadvantage of this sampling method. (4 marks}