12. In 2019 the mean tip left by customers at a bar was $3.20. Before the COVID the bar implemented a couple procedure and policy changes aimed at increasing the mean tip amount. In a sample of 55 bills the mean tip amount was $3.72 with a standard deviation of $2.84. Complete the test below using a 10% significance level. [12] a) Write the hypotheses using appropriate notation. b) Calculate the test statistic. c) Find the p-value in Stat Key or other source. d) Write the conclusion in the context of the