VantageScore conducted a sample of 220 American adults and found that the average credit score for an American adult is 698. From past data, the population standard deviation was 46. a. In words, define the random variables X and X-bar. b. State the distribution of X-bar and explain why. c. Calculate the error bound for a 95% confidence interval for mu. Then, construct the confidence interval and interpret its meaning in the context of the problem. Round to 3 d.p. d. How many additional American adults would we need to sample for the error bound to be 4