A cell phone company claims that the average time a person spends on their phone is 12.8 hours a week. A sample of unknown size of phone users was selected, and the mean time they spent on their phones was 12.2 hours in a week, with a standard deviation of 2.3 hours. Using a 90% confidence level, how many people would the company have to sample in order for their hypothesis to be true?   500   30   300   50

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