A radio station wants to know if residents in their area are in favor of a proposed tax increase. They invite listeners to call in to respond to the poll. A total of 645 of the 800 who responded were against the tax. The station calculated a 95% confidence interval and declared, "Between 77.9% and 83.4% of residents oppose the new tax."a. Because of the way the poll was conducted, the results are invalid.b. This is a valid interval, so the station must be right.c. We can't say for certain that between 77.9% and 83.4% of residents oppose the new tax because it is a 95% confidence interval.