4. An advertisement for a teeth-whitening product states it will whiten your teeth and remove stains in 30 days or your money back. A random sample of 22 customers were asked to try the product and provide a time stamp as to when they noticed their teeth met the claims of the product. Based on their feedback, the customers felt the product met its claims after an average of 30.7 days with a standard deviation of 1.86 days. a. Set up the null and alternative hypotheses for this scenario. b. Calculate the test statistic and p-value. c. Using a signicance level of 0.05, is the advertisement making a true statement? Why or why not? Explain your reasoning. d. Another 10 customers were sampled and combined with the original 22 customers there is now a sample mean of30.4 days with a standard deviation of 1.52 days. Reevaluate parts b and c. Did any errors occur in part c and, if so, what type? Explain your reasoning