hello expert, I need help in this question , thank you , I will pick up your answer if you do good, thank you very much

(bl An airline company conducts a passenger satisfaction survey in the ight from Hong Kong to Switzerland. All seats are occupied and there are 40 passengers seated in the First class, 80 passengers seated in the Business class and 200 passengers seated in the Economy class. The company plans to randomly select a sample of 40 passengers for the survey. (bi) Name a random sampling method to be used to ensure a close representation of the population without bias towards any class of passengers. (bii) Find the number of passengers should be selected from the First class and the Business class by using the method stated in (bi)