4. Regarding survey responses, people often hesitate to provide an affirmative answer. Suppose that in a population, 80% would truthfully answer "No" to a question, while 20% would truthfully answer "Yes." However, 70% of the individuals lie about their response. Let \( Y \) be the number of people who must be surveyed until the first affirmative ("Yes") response is obtained. Derive the probability distribution of \( Y \). (7%)