A marketing researcher wants to estimate the mean amount that visitors to a theme park spend per person per day using a 95% confidence interval. She knows that the standard deviation of this amount is $25. a)How large of a sample should the researcher select so that the estimate will be within $3 of the population mean?b)Suppose that sample of size n determined in part a is taken, and the corresponding sample mean is $90. Find the 95% confidence interval of the population mean.