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but still do not understand about the step of this question

can you please help ??

3. (a) i. ii. There are x elderly, 3 teachers, and 5 health care workers waiting in a line to receive their vaccination. How many different arrangements are possible if only the elderly must stand together? (3 marks) A box contains (X + 5) SinoVac, 5 BioNTech, and 9 AstraZeneca vaccines. If 9 vaccines are picked out at random without replacement, determine the probability that 4 SinoVac, 3 BioNTech and 2 AstraZeneca vaccines are drawn. (4 marks) (b) Hong Kong adults were asked whether or not they have ever shOpped online during COVID-lQ pandemic. The following table gives a two-way classication of the reSponses. Have Never Shepped Have ShoPped 30 90 ii. iii. Female 20 (60+ x) . If one adult is selected at randOm, nd the probability that this adult is a female or have shopped online. (4 marks) Given that the selected adult is a female, what is the probability that she has never shepped Online? (2 marks) Let M denote the event that the adult is male, and 5' denote the event that the adult has never shapped online. Are events M and 5' independent? Justify your answer. (4 marks) (c) Suppose (5 + x)% of the residents in a lockdown building have the COVID-IQ disease. There is a diagnostic test to detect the COVID-lQ disease, but it is not very accurate. Historical evidence shows that if a person actually has the disease, the probability that the test will indicate the presence of the disease is 0.8. For a person who actually does not have the disease, the probability for the test will indicate the presence of disease is 0.25. If a person is selected randomly from this lockdown building to perform the test, and the test results indicate the disease is present, what is the probability that this person actually does not have the disease? (8 marks)