In a city with three high schools, all the ninth graders took a Standardized Test, with these results: High School Mean score on test Number of ninth graders Glenwood 76 272 Central City 90 308 Lincoln High 66 178 The city's PR manager, who never took statistics, claimed the mean score of all ninth graders in the city was 77.3 , Of course, that is incorrect. What is the mean score for all ninth graders in the city? Round to one decimal place. mean of all ninth grader's scores =