Suppose that a restaurant launched a new advertising campaign in conjunction with a new menu

Suppose that a restaurant launched a new advertising campaign in conjunction with a new menu.  After one month they take a random sample of 250 bills (tables) and find an average bill of 73.4.  In that sample they also find the standard deviation is 38.6.  Conduct a hypothesis test to determine whether the new campaign and menu have increased the average bill above the previous average of 71.6.  Hint, the null hypothesis is that mu<=71.6 and we assume that the standard deviation is unkonwn so we use the estimate of 38.6 from the sample.  What is the test statistic? Answer to three decimal places.