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Question 18 (6 points) A water supplying company wished to estimate the average amount the private customers pay per month. A random sample of 25 customers' bills produced a sample mean of $30 and a sample standard deviation of $5. (Hint: In the previous question, $5 is the standard deviation of the whole population, while now $5 is a standard deviation of just a sample of 25 customers.) c) Find a 95% confidence interval for the population mean in this situation (that is, the situation of the previous question). Question 18 options: C 27.94Sus32.06{"version":"1.1","math":"27.94\\leq\\mu\\leq32.06"} C 2sus3("version":"1.1","math":"2\\leq\\mu\\leq3"} C 25.94sus35.06 {"version":"1.1","math":"25.94\\leq\\mu\\leq35.06"} 24sus32.35 {"version":"1.1","math":"24\\leq\\mu\\leq32.35") Question 19 (6 points) A medical research team is interested in estimating the mean systolic blood pressure among teenagers. From previous study, they do know that the population standard deviation is 10. How many teenagers should be sampled so that a 90% confidence interval will have a margin of error of 5? (Hint: Certainly, the answer should present an integer number.) Question 19 options: O 15 11 C C 10